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Pizzo, Leonardo <1977>. "Analisi dei processi di invasione di piante esotiche nei paesaggi costieri sabbiosi del Veneto." Doctoral thesis, Università Ca' Foscari Venezia, 2012. http://hdl.handle.net/10579/1204.
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Questo studio analizza gli effetti del disturbo (principalmente antropico, ma anche naturale) sul processo di invasione da specie aliene nei sistemi di dune costiere della regione Veneto. La ricerca è stata articolata su due livelli, uno focalizzato sui tratti morfologici e funzionali delle specie vegetali (native ed aliene) delle dune costiere, l’altro al livello di comunità vegetale. I risultati evidenziano che altezza, superficie fogliare e SLA grandi sono tratti che favoriscono la colonizzazione delle dune mobili costiere da parte delle specie più invasive. L’impatto antropico ha profondamente contribuito al degrado della qualità e funzionalità degli ecosistemi costieri, riducendo la resistenza che le comunità vegetali native sono in grado di opporre all’ingresso delle specie aliene invasive in condizioni di minor disturbo.This study analyses the effects of disturbance (mainly human, but also natural) on the process of invasion by alien species in the coastal dune systems of Veneto region. The research has been articulated into two levels, one focusing on morphological and functional traits of coastal dune wild species (natives and aliens) and the other on the plant community level. The results highlight that height, large leaf area and SLA are useful traits for the successful colonisation of the most invasive species along the mobile coastal dunes. Human impact has deeply contributed to the decay of the quality and functionality of coastal ecosystems, reducing the resistance native plant communities are able to oppose the arrival of invasive alien species under less disturbed conditions.
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Falvo, Laura. "Analisi dei fattori prognostici nei carcinomi papilliferi della tiroide: ruolo del sottotipo istologico e della istologica invasione vascolare." Doctoral thesis, La Sapienza, 2006. http://hdl.handle.net/11573/917181.
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GASPARINI, GIULIA. "Cancer-Glia interaction in perineural invasion in pancreatic cancer: identification of FGF-BP1 as a molecular target." Doctoral thesis, Università Vita-Salute San Raffaele, 2022. http://hdl.handle.net/20.500.11768/122891.
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Introduction Perineural invasion (PNI) is defined as the presence of cancer cells along nerves. PNI has its highest incidence in pancreatic ductal adenocarcinoma (PDAC), where it is present in 80-100% of patients and is a negative factor associated with increased cancer recurrence and diminished survival. During PNI, nerves and cancer form a unique microenvironment that promotes both cancer growth and neural remodeling. Several molecules have been described to promote PNI, like neurotrophins and chemokines. Schwann Cells (SCs), the main glial cells of the peripheral nervous system, infiltrate PDAC at the early stages of disease and provide a guide to cancer cells along nerves as well as promoting neurogenesis around tumor. Despite the clear contribution of SCs to PNI, the interactions between myelinated nerves, SCs and PDAC have been poorly investigated.
Objectives Study the reciprocal interactions between PDAC and nervous cells and develop a new score to better stratify and analyze the severity of PNI in patients.
Materials and methods: We analyzed how myelinated nerves and cancer cells interact and identified the molecules governing this interaction. We used SCs-neuronal cocultures and 2D cancer cells to recreate in vitro PNI. In addition, to evaluate more physiologically these interactions, we developed pancreatic organoids.
Results: Our results showed that neoplastic cells can induce profound alterations in myelinated cocultures, both by direct and paracrine contact. By secretome analyses, we selected potential candidates able to induce myelin degeneration and focused on FGF-BP1, a molecule involved both in cancer progression and nerve degeneration. By treating with recombinant FGF-BP1 and inhibiting its signaling, we suggested that FGF-BP1 mediates myelin degeneration induced by cancer cells.
Moreover, we showed that myelin degeneration promotes cancer cells growth, proliferation, migration and invasion. To reproduce these results in a more physiological setting, we developed pancreatic organoids, spheroids and organoids-nerve cocultures. We also established an in vivo model of PNI by orthotopically transplanting cancer spheroids that we are currently validating. Finally, we applied the newly developed PNI score to a population of 507 patients who underwent surgical resection for PDAC at San Raffaele Hospital.
Conclusions: We have rigorously analyzed the interactions between PDAC and nerve and identified a candidate that could become a new therapeutic target for PDAC patients. In addition, we have detailed the role of PNI specifically in PDAC, prompting a greater attention for PNI in clinical settings.Introduzione L'invasione perineurale (PNI) è definita come la presenza di cellule cancerose lungo i nervi. La PNI ha la sua più alta incidenza nell'adenocarcinoma duttale pancreatico (PDAC), dove è presente nell'80-100% dei pazienti ed è un fattore negativo associato ad un aumento della recidiva del cancro e ad una ridotta sopravvivenza. Durante la PNI, i nervi e il cancro formano un microambiente unico che promuove sia la crescita del cancro che il rimodellamento neurale. Diverse molecole sono state descritte per promuovere la PNI, come le neurotrofine e le chemochine. Le cellule di Schwann (SC), le principali cellule gliali del sistema nervoso periferico, si infiltrano nel PDAC nelle prime fasi della malattia e forniscono una guida alle cellule tumorali lungo i nervi, oltre a promuovere la neurogenesi intorno al tumore. Nonostante il chiaro contributo delle SC alla PNI, le interazioni tra nervi mielinizzati, SC e PDAC sono state poco studiate. Obiettivi Studiare le interazioni reciproche tra PDAC e cellule nervose e sviluppare un nuovo punteggio per stratificare e analizzare meglio la gravità della PNI nei pazienti. Materiali e metodi: Abbiamo analizzato come interagiscono i nervi mielinizzati e le cellule cancerose e identificato le molecole che governano questa interazione. Abbiamo utilizzato coculture neuronali-SC e cellule tumorali 2D per ricreare la PNI in vitro. Inoltre, per valutare più fisiologicamente queste interazioni, abbiamo sviluppato organoidi pancreatici. Risultati: I nostri risultati hanno mostrato che le cellule neoplastiche possono indurre profonde alterazioni nelle cocolture mielinizzate, sia per contatto diretto che paracrino. Mediante analisi del secretoma, abbiamo selezionato potenziali candidati in grado di indurre la degenerazione della mielina e ci siamo concentrati su FGF-BP1, una molecola coinvolta sia nella progressione del cancro che nella degenerazione dei nervi. Mediante trattamento con FGF-BP1 ricombinante e inibizione del suo segnale, abbiamo proposto che FGF-BP1 possa mediare la degenerazione della mielina indotta dalle cellule tumorali. Inoltre, abbiamo dimostrato che la degenerazione della mielina promuove la crescita, la proliferazione, la migrazione e l'invasione delle cellule tumorali. Per riprodurre questi risultati in un modo più fisiologico, abbiamo sviluppato organoidi e sferoidi pancreatici e coculture di organoidi-nervi. Abbiamo anche stabilito un modello in vivo di PNI trapiantando ortotopicamente sferoidi di tumore che stiamo attualmente convalidando. Infine, abbiamo applicato il nuovo punteggio di PNI ad una popolazione di 507 pazienti sottoposti a resezione chirurgica per PDAC presso l'Ospedale San Raffaele. Conclusioni: abbiamo analizzato rigorosamente le interazioni tra PDAC e nervo e identificato un candidato che potrebbe diventare un nuovo obiettivo terapeutico per i pazienti con PDAC. Inoltre, abbiamo dettagliato il ruolo della PNI specificamente nel PDAC, sollecitando una maggiore attenzione per la PNI in ambito clinico.
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David, Noemi. "Slow waves in un modello di crescita tumorale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12024/.
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In questo elaborato ho analizzato un sistema di reazione-diffusione proposto come modello per descrivere un fenomeno di crescita tumorale. In particolare, è stato approfondito il processo in cui l'invasione neoplastica è originata dalla produzione di un eccesso di ioni acidi da parte delle cellule maligne. Il sistema preso in esame descrive l'andamento di tre grandezze: la concentrazione di tessuto sano, la concentrazione di tessuto maligno e l'eccesso di ioni acidi. Ho quindi cercato soluzioni compatibili con il sistema le quali fossero funzioni della tipologia travelling waves, ossia onde che si propagano lungo l'asse reale con un grafico fissato e ad una velocità costante.
I risultati ottenuti in questo lavoro sono stati così suddivisi: nel Capitolo 1 viene descritto il processo di invasione tumorale dal punto di vista biologico, nel Capitolo 2 vengono forniti alcuni lemmi e proposizioni preliminari, nel Capitolo 3 viene calcolata un'approssimazione della soluzione del sistema tramite onde del tipo slow waves e infine nel Capitolo 4 sono state studiate la presenza e la larghezza dello spazio interstiziale, ossia di una regione situata tra il tessuto sano e quello neoplastico nella quale si registra una concentrazione di cellule, sia normali sia maligne, praticamente nulla. Infine, sono state rappresentate graficamente le soluzioni in tre possibili situazioni caratterizzate da un diverso parametro di aggressività del tumore.
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Masi, Alessia. "Targeting integrins and modulating invasion and metastasis with metal-based drugs." Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3615.
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2008/2009Distant metastases of solid tumours are the major cause of cancer death. To improve the effectiveness of chemotherapy, only marginally active on secondary tumours, anti-metastatic agents are needed, i.e. compounds that display the capacity to selectively interfere with metastatic formation and growth. Among metal compounds, NAMI-A, HIm[Ru(III)Cl4Imdmso], has repeatedly shown a peculiar and selective anti-metastatic activity being able to prevent the formation, and to inhibit the growth of established secondary tumours. On these bases, the first phase of the project was aimed to investigate how variations on the NAMI-A chemical structure can influence the anti-metastatic activity. For this purpose, some representative complexes have been chosen: two heterocyclic compounds KP418, HIm[Ru(III)Cl4(Im)2], and KP1019, HInd[Ru(III)Cl4(Ind)2], presenting a different N-donor ligand, and three organometallic compounds, RM175, [(η6-biphenyl)Ru(II)Cl-(ethylendiamine)]PF6, its osmium congener AFAP51, [(η6-biphenyl)Os(II)Cl(ethylene-diamine)]BF4, and RAPTA-T, [RuCl2(η6-toluene)PTA], carrying a PTA ligand instead of ethylendiamine. The effects of the compounds on the interference with some steps of the metastatic progression are evaluated with appropriate in vitro tests, comparing the behaviour of the human MDA-MB-231 highly invasive breast cancer cells to that of human HBL-100 non tumorigenic mammary epithelial cells. To validate the model, the in vitro effects are compared with the in vivo anti-metastatic activity studied in the MCa mammary carcinoma of the CBA mouse. The results obtained highlight the selective activity of the organometallic compound RAPTA-T towards the highly invasive cell line in vitro, accompanied by a selective inhibition of metastasis development in vivo. RAPTA-T seems to act through the modulation of tumour cells-extracellular matrix interactions, and of cell motility. In particular RAPTA-T induces a cytoskeleton remodelling, mainly through the formation of stress fibres, that causes a stiffening of the cell body, particularly evident on MDA-MB-231 cells grown on ECM components. These effects, selectively identified in the highly invasive MDA-MB-231 cells, can be related to the higher ruthenium uptake, detected in this cell line. Cell adhesion, migration and invasion are directly related to actin assembly and disassembly, phenomena regulated by the RhoGTPases. RAPTA-T completely counteracts the increase of trypsin mediated cell detachment induced by the RhoGTPases inhibitor C3 transferase, in MDA-MB-231 cells grown on fibronectin and collagen IV, and on HBL-100 cells grown on collagen IV. These molecular events might stem from the cell surface and involve integrin adhesion molecules, as suggested by the role of ECM components in the functional tests and by the preference of RAPTA-T to bind them, above all, collagen IV, with which RAPTA-T interacts chemically as confirmed by an NMR analysis. The effect of RAPTA-T on cells immediately after the adhesion on the substrate, i.e. mainly adherent with integrinic receptors, suggests that RAPTA-T interacts mainly with integrins in the form already bound with the substrate. Le metastasi dei tumori solidi sono una delle principali cause di morte. Per migliorare l’effetto della chemioterapia, che è attiva solo marginalmente sui tumori secondari, sono necessari agenti anti-metastatici, cioè composti che si mostrino capaci di interferire selettivamente con la formazione e la crescita delle metastasi. Tra i vari composti di sintesi il NAMI-A, HIm[Ru(III)Cl4Imdmso], ha ripetutamente mostrato una selettiva azione anti-metastatica dimostrandosi capace di prevenire la formazione e di inibire la crescita di metastasi già formate. Su queste basi, la prima fase di questo progetto ha avuto lo scopo di indagare come variazioni nella struttura chimica del NAMI-A potessono influenzare l’azione anti-metastatica. A questo scopo sono stati scelti alcuni composti rappresentativi: due composti eterociclici il KP418, HIm[Ru(III)Cl4(Im)2], e il KP1019, HInd[Ru(III)Cl4(Ind)2], e tre composti organometallici, RM175, [(η6-biphenyl)Ru(II)Cl-(ethylendiamine)]PF6, il suo congenere a base di osmio AFAP51, [(η6-biphenyl)Os(II)Cl(ethylene-diamine)]BF4, e RAPTA-T, [RuCl2(η6-toluene)PTA], che al posto dell’etilendiamina presenta il ligando PTA. Gli effetti dei composti sull’interferenza con alcuni step della progressione metastatica sono stati valutati con alcuni test in vitro, paragonando il comportamento della linea cellulare altamente invasiva MDA-MB-231 proveniente da carcinoma mammario, con quello delle HBL-100 linea cellulare dell’epitelio mammario non tumorigenica. Per validare il modello proposto in vitro gli effetti dei composti sono stati paragonati con la loro azione in vivo studiata sul carcinoma mammario (MCa) dei topi CBA. I risultati ottenuti mettono in luce la selettiva azione del composto organometallico RAPTA-T verso la linea cellulare altamente invasiva in vitro, accompagnata dalla inibizione selettiva dello sviluppo delle metastasi in vivo. Il RAPTA-T sembra agire attraverso la modulazione delle interazioni cellula-matrice extracellulare e della motilità cellulare. In particolare il RAPTA-T induce il rimodellamento del citoscheletro, principalmente attraverso la formazione di fibre da stress, questo genera irrigidimento del corpo cellulare, particolarmente evidente sulle MDA-MB-231 cresciute sui componenti della matrice extracellulare. Questi effetti, selettivamente identificati sulla linea altamente invasiva, MDA-MB-231, possono essere correlati ad un più alto assorbimento di rutenio che è stato rilevato in questa linea cellulare. L’adesione cellulare, la migrazione e l’invasione sono direttamente correlate al rimodellamento del citoscheletro actinico, e questi fenomeni sono regolati dalle RhoGTPasi. Il RAPTA-T reverte completamente l’aumentato distacco conseguente al trattamento con la C3 transferasi, agente che inibisce le RhoGTPasi, nelle MDA-MB-231 cresciute su fibronectina e collagene IV e sulle HBL-100 cresciute sul collagene IV. Questi eventi potrebbero coninvolgere l’adesione integrinica ai substrati, come suggerito dal ruolo dei componenti della matrice extracellulare nei test funzionali presi in considerazione, dalla preferenza del RAPTA-T per il legame con questi, e soprattutto il collagene IV con cui il RAPTA-T interagisce chimicamente, come confermato dall’analisi NMR. L’effetto del RAPTA-T su cellule appena dopo l’adesione al substrato, quindi prevalentemente legate attraverso i recettori integrinici, suggerisce che il RAPTA-T interagisca principalmente con le integrine nella forma già legata i substrati.
XXII Ciclo
1978
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White, Laura Linsey Fallaize. "Mechanisms underlying marine macroalgal invasions : understanding invasion success of Sargassum muticum." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23713.
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This thesis examines different aspects of invasion success of the brown macroalga Sargassum muticum. Chapter two investigates the relationship between native diversity and invasibility by S. muticum in experimental and unmanipulated communities of low intertidal macroalgae. I found that diversity effects on invasion varied from positive to negative with life history stage of the invader. Native diversity facilitated recruitment of S. muticum, but decreased growth and or survivorship. Phenological differences between S. muticum and native macroalgal species may contribute to the success of this invader in British Columbia.
Chapter three explores the effects of S. muticum on native macroalgal diversity at different densities by manipulating exotic density in natural communities. I found that the effects of S. muticum on native macroalgal richness were both density and time dependent, and are mediated through competition for light. The reciprocal interaction between S. muticum and native macroalgal diversity has shown effects in both directions, and suggest some degree of symmetry in the interaction between non-native S. muticum and native macroalgae.
Chapter four examines whether non-native S. muticum is less grazed than native macroalgae in British Columbia, and whether the concentrations of defensive polyphenolic compounds in the tissue of the exotic differ from native conspecifics. In contrast to the predictions of the Enemy-Release Hypothesis, I showed that when presented a choice, native herbivores do not discriminate between native and non-native macroalgae. The levels of polyphenolic defenses in the exotic were similar to some native macroalgae, suggesting differences in polyphenolic concentrations are not influencing herbivore choice. Reduced grazing of non-native S. muticum by native herbivores is not contributing to the success of this invasive in British Columbia.
Chapter five tests two predictions of the Evolution of Increased Competitive Ability hypothesis; whether S. muticum in non-native regions attains greater sizes and lower chemical defenses than conspecifics in the native region. We compared the size (as a measure of performance) and levels of polyphenolic defenses of S. muticum from its native and invaded regions. My preliminary results suggest that in non-native regions, S. muticum attains larger sizes with lower levels of defensive polyphenolic compounds than native regions.
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Shucksmith, Richard. "Biological invasions : the role of biodiversity in determining community susceptibility to invasion." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485655.
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Invasion by non-native species has the potential to change native biodiversity, community structure, food webs and interactions between species.. Small scale manipUlative experiments :using sessile organisms have shown that increasing biodiversity reduces community susceptibility to invasion by non-native species. However, large scale observational studies have shown that some ofthe most diverse systems are the most invaded. The search fora generalised mechanism that may make a resident community resistant to invasion by a non-native species has proven difficUlt and has provided contrasting resUlts. Small scale experiments have been criticised for their dinllnptive spatial scale and -rdatively homogeneous environmental conditions. _ The contrasting results between the experimental and observational studies may be due to the heterogeneous nature ofmost environments which iilllY promote invasion as well as coexistence. In this thesis I study the relationship between invasion and competition in heterogeneous en'ir0nments using the North-East Asian amphipod Caprella mutica. Caprellids have been shown to live on marine sessile species such as, algae, hydroids, tunicates, mussels, bryozoans and sponges which attach to a hard substratum and form '. . erect structures that project into the wat~r column. Species-rich epifaunal comm.unities . can create a structurally diverse habitat. In choice experiments using different structural patches and structure types in the laboratory, there was no effect ofthe number of different types ofstructures in a patch on the number of C. mutica attached to a patch, but structure type was critically important. Caprella mutica preferred the filament.ous structures long t¢and short turf .over mussel mimics. In field experiments, densities were 7 times greater than the laboratory experiments.. There were twice as many caprellids on the structurally heterogeneous patches than on the structurally homogeneous patches. However, invasion patterns in the field did follow the same structure type as the laboratory experiments. Intraspecific competition appeared to be stronger on the homogeneous patches, whereas there were more refuges and microhabitats on the heterogeneous patches and this may have reduced the aggressive interactions between conspecifics. Artificial and live habitats were placed together in laboratory experiments and there was .t'. no difference in the number of caprellids attached to the artificial and live habitats. Lack ofdifferences between live biota and the artificial mimics showed that C. mutica habitat choice is most likely due to the physical characteristics ofthe habitat. Furthermore, choice oftype ofstructure did not differ betWeen the artificial and live patches. I In competition experiments between C. mutica and two native cap~ellids Caprella linearis and Pseudoprotella.phasma, C. mutica successfully displaced both species from homogeneous artificial habitat patches after 24 hours. Patches that had a refuge attached reduced the number of C. linearis being displaced but only when C. mutica was at a low density. Further experiments, using 3 different levels of structural heterogeneity with C. linearis .and C. mutica, showed that the two species could occupy the structurally heterogeneous patches at similar densities after the 24 hour experimenta~ period. On structurally homogeneous patches C. mutica significantly displaced C. linearis. Aggressive interactions were likely to have been more intense on the homogeneous than structurally heterogeneous patches and this study suggests that C. mutica displaces C. linearis through agonistic interactions. The same processes that reduced intraspecific competition in the first set ofexperiments also promoted coexistence between the two ecologically similar species. Consequently, structurally diverse habitats have the potential to promote invasion while at the same time reducing the impact of an invader on native species. Kelp communities consisting ofLaminaria hyperborea and Saccharina latissima in close proximity to known populations of C. mutica were surveyed and showed that C. mutica did disperse to the kelp communities but was not found on any ofthe kelp plants in the upper zone of the kelp bed. This study was limited to only sampling kelp plants to a depth of 1 to 2 m on spring tides and it is possible that C. mutica may inhabit kelp ' . plants that are deeper. However, laborat~ experiments showed Carcinus maenas predated on C. mutica and may provide biotic resistance to benthic emjronments from 'the invasion by C. mutica. Even at small spatial scales where environmental conditions were similar for both the laboratory and field experiments, the probability of invasion cannot be predicted ' reliably from aggregate community 'measures such as species richness (analogous to the number ofdifferent types ofstructures). Individual characteristics ofthe invading ,' species and positive'associations with structure types, even at small spatial scales, may increase the probability ofinvasion regardless of species richness. Thus, invasion by C. mutica is likely if an appropriate structure type is prese.nt and the success ofinvasion increases with an increasing richness of structure-forming epibiota. For native fauna, which have a similar ecological requirement to the invader, structural heterogeneity appears to reduce the impact ofthe invading species. Habitat heterogeneity may be essential for co-existence between a superior and inferior competitor, as structurally complex habitats offer a variety of different microhabitats and niches. The invasibility of a community, therefore, depends on the diversity and composition of the community being invaded, and the invasive potential of a species depends not only on the community properties, but also on the characteristics of the invader.
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Miller, Nathaniel P. "Invasions of Secondary Forest by a Nonnative Grass Species: Microstegium vimineum {Nees}(Poaceae)." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1307047314.
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Medvecz, Erin. "Resisting Invasion: Grassland Plant Responses to an Invasive Legume, Lespedeza cuneata." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2123.
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Invasive species, including Lespedeza cuneata (Dum. Cours.) G. Don, threaten the success of grassland restoration through their ability to alter species composition following invasion. Combining the filter framework model of community assembly with the passenger-driver model of non-native species behavior can clarify the broader impacts of invasive species in the communities they invade. Testing this combined theory by exploring the mechanisms by which an invasive functions (above- and belowground) and the response of native plants from different functional groups to these mechanisms can reveal if an invasive functions as a driver and a filter. Observational field surveys were conducted across fifteen L. cuneata-invaded grasslands to compare species composition of plots in which L. cuneata was either present or absent. In a greenhouse experiment, the response of natives in three functional groups—grasses, forbs, and legumes—to aboveground (competition), belowground (soil conditioning), and both above- and belowground interactions with L. cuneata were investigated. Response variables (height, leaf number, root length, biomass, specific leaf area, leaf chlorophyll, and soil pH and conductivity) were measured. Regional analysis of the field surveys did not identify distinct species compositional differences in invaded and uninvaded areas, while within-site analyses revealed differences in half of the sites, suggesting that site specific characteristics could be impacting whether L. cuneata presence corresponds with a fundamental shift in species composition. Regionally, grass and legume abundance was higher in plots not containing L. cuneata than in plots where it was present. The greenhouse experiment illustrated stronger aboveground competitive effects than belowground soil effects, with impacts differing among functional groups. Under pressure of competition with L. cuneata, grasses experienced increases in certain measured traits (height, root length and specific leaf area), while when grown in conditioned soil, grasses produced greater biomass. Additionally, the growth of L. cuneata differed when grown in competition with forbs, grasses, and legumes. Competition with legumes resulted in the most suppressed growth of L. cuneata individuals among the three functional groups. Considering the field survey and greenhouse experiments in conjunction suggests that grasses can benefit from interactions with L. cuneata and have the potential to outcompete and exclude it, while legumes are detrimental to the growth of L. cuneata and compete for niche space, resulting in L. cuneata establishment in legume-poor areas. The forb functional group did not have a significant relationship to L. cuneata presence in either the field surveys or the greenhouse experiment. Lesepedeza cuneata acts as a driver, altering the abiotic and biotic filters to impact species composition, while it does not act as a filter, with native grasses and legumes acting to filter the L. cuneata.
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Nati, Julie Jeanne Helene. "Invasion physiology : do physiological characteristics facilitate the spread of invasive fish species?" Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8104/.
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A considerable number of abiotic (e.g. temperature) and biotic factors (e.g. intra-interspecific interactions) contribute in shaping species’ distribution and invasiveness but knowledge is still lacking regarding the importance of physiological and behavioural traits in determining the distributions of ectotherms and especially the invasion success of non-native species into novel habitats. With rising temperatures, distribution shifts in many of fish species have been observed. Additionally, changing thermal conditions are facilitating the colonisation of invasive species. It is crucial that we gain an increased understanding of the mechanisms underlying the effects of environmental change on the distribution of aquatic species and the ecological damage caused by invasive species. Physiological traits are likely to present a fundamental constraint on the environments that are habitable to a given species. Whole animal traits associated with energy metabolism and locomotory performance are especially likely to be important in this regard. Nevertheless, the effects of traits such as metabolic rate and aerobic scope (AS) on the distributions of native and invasive species have not been thoroughly studied. In a first step toward understanding these effects, I performed a phylogenetically-informed analysis of links between AS and absolute latitudinal distribution range in 86 fish species. From the results obtained in Chapter 2, I found no evidence for the direct implication of AS in the currently observed distributions of fishes. Moreover, no association between AS and invasion success in 59 freshwater fish species (23 invasive and 36 native species) was found. These results suggested that peak AS is not a constraining or determining factor in the distribution range and invasion success in fish. Following on from these results, there is a possibility that there could be a trade-off between peak and breadth of performance for AS across temperatures in fishes. Species with a higher peak AS might only be able to function normally over a narrow range of temperatures. In Chapter 3, I collected AS data from literature and conducted phylogenetical-informed analysis to test the trade-off theory in AS across 28 fish species. No evidence could be found for a trade-off between peak and breadth performance in AS for fish. Interspecific competition between invasive and native fish species might cause changes in the structure of native fish communities. Furthermore, these interactions can vary over competitive context (e.g. for prey or cover), differ over a range of environmental factors (e.g. in response to temperature variation) and be linked directly or indirectly to species’ metabolic capacity (e.g. aerobic scope). With increasing temperatures, invasive species might gain a competitive advantage over the native species though shifts or changes in competitive behaviour and traits such as AS. After having investigated broad patterns among AS and geographical distributions in fishes, the remainder of my thesis focused on trade-offs in energy allocation and tolerance to environmental stressors in a pair of species to determine the role of aerobic capacity as a factor in competition between these two species. Specifically, I examined interactions between native stone loaches (Barbatula barbatula) and invasive bullheads (Cottus gobio), two species which occupy the same ecological niche and that are believed to compete for similar habitats. Physiological and behavioural traits could play an essential role in the spread of invasive species, particularly the internal underlying mechanisms that modulate an organism’s response to environmental changes. In Chapter 4, I examined physiological and behavioural responses of invasive bullheads and native stone loaches to acute and acclimated temperature shifts (13-21°). I found that invasive bullheads had a lower AS than stone loaches over all temperatures tested. Bullheads were also less active overall and preferred colder temperatures (17.5-19°C) than stone loaches (21-22.4°C). Therefore, changes in AS in response to thermal variation are unlikely to be a contributing factor in invasion success of bullheads in Scottish rivers. In Chapter 5, I investigated the direct competitive interactions between bullheads and stone loaches at three different temperatures (13°C, 17°C and 21°C). Overall, native stone loaches were better competitors for shelter use and in particular at colder temperatures. There was no clear causal effect of temperature or AS on competitive outcomes between these two species. Low competitive ability found in invasive bullheads suggests that bullheads may not be actively displacing stone loaches. It has been suggested that a successful invader should have a wide tolerance range for different environmental factors. For example, invasive species might be more tolerant to hypoxic events as compared to native species. In Chapter 6, I looked at the hypoxia tolerance and avoidance behaviour of bullheads and stone loaches over different dissolved oxygen (DO) concentrations (100%, 80%, 60%, 40%, 30%, 25% and 20% DO levels). Surprisingly, I found that bullheads were less tolerant to hypoxic conditions with a Pcrit value of 4.96 mg O2 l-1 at 14°C. Avoidance behaviour towards progressive hypoxia was similar between bullheads and stone loaches; both species spent most of their time utilising the shelter even in hypoxic conditions. Low tolerance towards hypoxia did not give an advantage to invasive bullheads over native stone loaches in particular during harsh environmental conditions. The results from this thesis suggest that metabolic traits may not play as strong a role in constraining species distributions as previously suspected, particularly in the specific case of interactions between native stone loaches and invasive bullheads in Scotland. Instead, other physiological factors, life history traits, and population demographics may play a primary role in affecting invasion success in this case.
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Porter, Erica. "The roots of invasion: Belowground traits of invasive and native Australian grasses." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134392/1/Erica_Porter_Thesis.pdf.
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Non-native grasses, originally introduced for pasture improvement, threaten Australia's iconic low-resource grasslands and a thorough understanding of the life-history strategies associated with these species is essential for effective management. Comparing invasive qualities across four congener pairs of native and non-native grasses, it was revealed that non-natives displayed a unique combination of morphological and physiological traits compared to natives. This study applied a novel technique of microdialysis and found that native and non-native grasses use soil nitrogen differently, likely contributing to the competitive advantage shown by non-native grasses across Australia.
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Heger, Tina. "Zur Vorhersagbarkeit biologischer Invasionen : Entwicklung und Anwendung eines Modells zur Analyse der Invasion gebietsfremder Pflanzen /." Berlin : Inst. für Ökologie der Techn. Univ, 2004. http://www.gbv.de/dms/bs/toc/472604457.pdf.
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Ndwayana, Hamilton Ncedo. "A sustainable development approach in the control of alien invasion vegetation." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020803.
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Invasive alien tree species have negative environmental and economic impacts throughout the world. For example, black wattle (Acacia mearnsii) threatens native habitats by competing with and so repressing or excluding indigenous vegetation: in this way it replaces grass communities, reduces biodiversity, and increases water loss from riparian zones, thereby fundamentally damaging the ecosystem. The Acacia mearnsii threat requires urgent attention: effective control and management is urgently required if these deleterious impacts are to be reversed or prevented. The present study was conducted in the Elliot and Ugie communities situated in the Sakhisizwe and Elundini Local Municipalities. The objective of this study was to design integrated, efficient and cost-effective methods to help farmers and members of these communities with control and management of alien plant invasions. Further the study aimed to evaluate the implementation and efficacy of Working for Water (WfW) initiatives in poverty alleviation, and skills development: in addition the study attempted to assess WfW inputs as regards relevant legislation aimed at combating major wattle invasions. Mixed methodological approaches were employed, utilizing both qualitative and quantitative techniques. Questionnaire surveys, semi-structured interviews, use of photos, content analyses of local documents and experimental field work were all employed in order to collect and interpret data for the study. The study reveals that mechanical control and rehabilitation in combating should provide efficient and cost-effective methods for proper management of rangelands. Moreover the National Department of Agriculture, Forestry and Fisheries (DAFF) should be urged to devise and enforce legislation that will help to ensure sustainable control and management of black wattle through conservation of the natural environment. Furthermore funds should be made available for wattle eradication programmes so as alleviate poverty by creating more job opportunities for members of poor communities.
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Carol, Bruguera Joaquim. "Ecology of an invasive fish (Silurus glanis) in Catalan reservoirs." Doctoral thesis, Universitat de Girona, 2007. http://hdl.handle.net/10803/7870.
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L'objectiu d'aquesta tesi és aportar les primeres dades sobre l'ecologia del silur (Silurus glanis) introduït a la Península Ibèrica i estimar els seu impacte ecològic sobre la biota nativa. Es van mostrejar les comunitats de peixos de 14 embassaments catalans. El silur es troba actualment introduït a quatre conques Ibèriques: a la de l'Ebre fa uns 30 anys, a les del Ter i Tajo fa uns pocs anys i recentment al Llobregat. Hem demostrat la utilitat de comparar estadis d'invasió recents i avançats per mirar d'entendre els canvis ecològics causats per espècies invasores: les introduccions recents presenten silurs més joves, de menor mida i amb taxes de creixement superiors a les de les poblacions introduïdes anteriorment i també respecte les poblacions natives; a més, depreden majoritàriament sobre peixos, en contra de les poblacions més antigues que s'alimenten sobretot de cranc. Finalment, aportem les primeres dades publicades de telemetria del silur.The aim of this thesis is to provide the first data on the ecology of European Catfish (Silurus glanis) introduced to the Iberian Peninsula and to appraise its ecological impact on native biota. We sampled the fish assemblage of 14 Catalan reservoirs (Spain). The European catfish is nowadays introduced in four Iberian river basins: in the Ebro river basin for 30 years, in the Ter and Tajo river basin for a few years and we report the first record for the Llobregat river basin. We demonstrate the utility of comparing early and late invasion stages to understand the ecological changes caused by invasive species: recent introductions of catfish had smaller and younger catfish with growth rates higher than old and native populations and preying on fish instead of crayfish for old introductions. We also report the first published telemetry data for catfish.
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Moodley, Desika. "Determinants of introduction and invasion success for Proteaceae." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79851.
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Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Successful biological invasions take place when species introduced to regions outside their natural dispersal range overcome several barriers and establish, persist, proliferate and spread potentially resulting in major threats to biodiversity. The success of invasive alien plants depends on species-specific traits and characteristics of the introduced environment. In this thesis I explore which species traits are important and which environmental barriers need to be overcome for an invasion to occur using Proteaceae as a test case. Firstly, I assessed the global introduction history and invasion ecology of Proteaceae - a large plant family with many taxa that have been widely disseminated by humans, but with few known invaders. This revealed that at least 402 species (i.e. 24% of 1674 species in this family) are known to have been moved by humans out of their native ranges, 58 species (14%) have become naturalized and 8 species (2%) are invasive. The probability of naturalization was greatest for species with large native range sizes, low susceptibility to Phytophthora root-rot disease, larger seeds, mammal-dispersed seeds and those with the capacity to resprout after fire or other disturbances. The probability of naturalized species becoming invasive was greater for species with larger range sizes, species used as barrier plants, taller species, species with smaller seeds, serotinous species, and those that regenerated mainly through re-seeding. Secondly, I looked at mechanisms underlying naturalization on a regional scale, using species which are not already classified as major invaders. At least 26 non-native Proteaceae species have been introduced to, and are cultivated in, South Africa. Propagule pressure facilitated the naturalization of Hakea salicifolia populations in climatically suitable areas, but in suboptimal climates human-mediated land disturbance and land management activities are important for naturalization. Similar drivers are important for naturalization of other alien Proteaceae: a long residence time, fire regimes, poor land management, and propagule pressure were important mechanisms for naturalization. Thirdly, I determined whether reproduction, which in part drives propagule pressure, serves as a barrier for naturalization. I examined several Australian Proteaceae species introduced to South Africa and observed that all species were heavily utilized by native nectar-feeding birds and insects. The five Banksia species that were assessed are self-compatible but four species have a significantly higher reproductive output when pollinators visit inflorescences. Fruit production in H. salicifolia does not differ between naturally-pollinated and autonomously-fertilized flowers. Moreover, no significant difference in fruit production was observed between the five pollination treatments (i.e. natural, pollen-supplementation, autonomous, hand-selfed and hand-crossed treatments) and naturalized and non-naturalized populations. However, pollen limitation was detected in non-naturalized populations which received fewer pollinator visits than naturalized populations. Thus, reproduction limits but is not a fundamental barrier to invasion for H. salicifolia. I conclude that reproductive success of the studied Proteaceae, which is a key barrier determining invasiveness, is not limited by autonomous seed set or mutualisms in the introduced range. In this thesis I highlight biogeographical characteristics, a set of life-history traits and ecological traits as important determinants of invasiveness. These traits are in turn dependent on the stage of invasion. Characteristics of the recipient environment are also important drivers of invasions. This study provides a better understanding of plant invasions in general, but the patterns and processes of invasions highlighted in this thesis will be particularly useful for the current and future management of alien Proteaceae in South Africa and elsewhere, as well as, other species that are adapted to Mediterranean and nutrient poor ecosystems. For example, combining traits of invasiveness and susceptible environments will help to identify which non-native species pose a high risk of becoming invasive (e.g. species with large home ranges and barrier plants) and which conditions in the target area are likely to facilitate or exacerbate invasions (e.g. strong climate match and high propagule pressure).
AFRIKAANSE OPSOMMING: Suksesvolle biologiese indringing vind plaas wanneer ʼn spesie geïntroduseer word in ʼn area buite sy natuurlike verspreidings area, sekere versperrings oorkom, vestig, bly voortbestaan, vermenigvuldig en versprei en potensieel ʼn groot bedreiging inhou vir biodiversiteit. Die sukses van uitheemse indringer plante hang af van spesifieke kenmerke van die spesie en kenmerke van die omgewing waarin dit geïntroduseer word. In hierdie tesis maak ek gebruik van Proteaceae om te ondersoek watter kenmerke is belangrik en watter omgewing versperrings moet oorkom word vir indringing om plaas te vind. Ten eerste assesseer ek die wêreldwye introduksie geskiedenis en indringers ekologie van Proteaceae – ʼn groot plant familie wat wyd gebruik word deur mense, maar met min indringer spesies. Dit het gewys dat mense ten minste 402 spesies (dus 24% van die 1674 spesies in die familie) uit die inheemse areas verskuif het, 58 spesies (14%) genaturaliseer het en 8 spesies (2%) indringers geword het. Die moontlikheid van naturalisasie was die grootste vir spesies met ʼn groot inheemse streek, lae vatbaarheid vir Phytophthora wortelvrot, groter sade, dier verspreide sade en die met ʼn vermoë om weer uit te spruit na ʼn vuur of ander versteuring. Die moontlikheid van genaturaliseerde spesies om indringers te word, was groter vir spesies met groter streek grootte, spesies wat as versperring plante gebruik word, hoër spesies, spesies met kleiner sade, serotiniese spesies, en die wat hoofsaaklik voortbestaan as saadspruiters. Tweedens, het ek gekyk na onderliggende meganismes op ʼn regionale skaal, deur gebruik te maak van spesies wat nie alreeds as belangrike indringers geklassifiseer is nie. Ten minste 26 nie-inheemse Proteaceae spesies is alreeds geïntroduseer en word gekultiveer in Suid Afrika. Propaguul druk fasiliteer die naturalisering van Hakea salicifolia populasies in areas met geskikte klimaat, terwyl in areas met ʼn sub optimale klimaat, versteurings deur mense en grond bestuurs aktiwiteite belangrik is vir naturalisering. Die selfde drywers is belangrik vir die naturalisering van ander uitheemse Proteaceae: lang verblyftyd, vuur bestel, swak land bestuur en propaguul druk. Derdens het ek bepaal of reproduksie, wat gedeeltelik propaguul druk dryf, ʼn versperring is vir naturalisasie. Ek het gekyk na verskeie Australiese Proteaceae spesies wat geïntroduseer is in Suid Afrika, en het gevind dat al die spesies besoek word deur inheemse nektar etende voëls en insekte. Die vyf Banksia spesies wat geassesseer is, kan self bestuif, maar vier van die spesies het ʼn betekenisvolle hoër reproduksie wanneer bloeiwyses deur bestuiwers besoek word. Vrug produksie verskil nie tussen natuurlik bestuifde en self bestuifde blomme in H. salicifolia nie. Verder was daar geen verskil tussen vrug produksie van die vyf bestuiwings behandelinge (naamlik: natuurlik, stuifmeel bygevoeg, self, hand self en hand kruis) en tussen genaturaliseerde en nie genaturaliseerde populasies. Ewenwel, stuifmeel beperking is gevind in nie-genaturaliseerde populasies wat egter ook minder besoeke ontvang het dan die genaturaliseerde populasies. Dus, reproduksie kan die verspreiding beperk maar is nie ʼn fundamentele versperring vir indringing van H. salicifolia nie. My konklusies is dat die reproduktiewe sukses, wat andersins ʼn sleutel versperring is vir indringing, in die bestudeerde Proteaceae nie beperk word deur outonomiese saad produksie of mutualismes in die geïntroduseerde gebied nie. In hierdie tesis beklemtoon ek die biogeografiese karakters, lewens geskiedenis kenmerke en ekologiese kenmerke as belangrike bepalers van indringing. Hierdie kenmerke is op hulle beurt weer afhanklik van die stadium van indringing. Karakters van die ontvangende omgewing is ook belangrike dryfvere van indringing. Hierdie studie verbeter hoe ons plant indringing in die algemeen verstaan, maar die patrone en prosesse van indringing wat beklemtoon word in hierdie tesis sal besonder bruikbaar wees vir huidige en toekomstige bestuur van uitheemse Proteaceae in Suid Afrika en op ander plekke, asook vir ander spesies wat aangepas is tot Mediterreense en nutriënt arm ekosisteme. Byvoorbeeld, die kombinasie van kenmerke van indringing en vatbare omgewings sal help om te identifiseer watter uitheemse spesies ʼn hoë risiko inhou om ʼn indringer te word (byvoorbeeld spesies met ʼn groot streek grootte en versperring spesies) en watter kondisies in die teiken area die waarskynlikste indringing fasiliteer of vererger (byvoorbeeld sterk klimaat ooreenstemming en hoë propaguul druk).
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Carmona, Catot Gerard. "Explaining the invasive success of the eastern mosquitofish (Gambusia holbrooki): the role of temperature." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/129501.
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The eastern mosquitofish (Gambusia holbrooki) is one of the most widely distributed and invasive inland fish. It is known that it has not been established in northern Europe or upstream of rivers, where the temperature is too low for survival and reproduction. This thesis examines how temperature affects the competitive ability and life history traits of mosquitofish. We sampled mosquitofish along latitudinal gradients and along rivers and we found that mosquitofish in more favorable environments (i.e. low latitudes and downstream river reaches) had a higher reproductive effort and lower body condition but these patterns of variation were weak and dependent on fish age. We also carried out an experiment which showed that as the temperature rises mosquitofish increases its competitive ability for resources and its aggressive behavior towards Aphanius iberus, an endangered Iberian endemism. Our results imply that climate change will favor the invasive success of mosquitofish and will increase its impact on native fishLa gambúsia (Gambusia holbrooki) és un dels peixos continentals més àmpliament distribuït i més invasors. Se sap que no s’ha pogut establir al nord d’Europa ni a trams alts de rius, on la temperatura és massa baixa per a la supervivència i la reproducció. Aquesta tesi analitza com afecta la temperatura a la capacitat competitiva i a les característiques del cicle vital de la gambúsia. Es van mostrejar gradients latitudinals i al llarg de rius i es va trobar que la gambúsia que vivia a ambients més favorables (és a dir, latituds menors i zones baixes dels rius), presentava un major esforç reproductiu i una menor condició corporal però que aquests patrons de variació eren febles i depenien de l'edat dels peixos. També es va portar a terme un experiment en què es va demostrar que a mesura que puja la temperatura la gambúsia incrementa la seva capacitat de competència pels recursos i el comportament agressiu contra el fartet (Aphanius iberus), endemisme ibèric en perill d'extinció. Els nostres resultats impliquen que el canvi climàtic afavorirà l'èxit invasor de la gambúsia i augmentarà el seu impacte en els peixos natius
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Barrios-O'Neill, Daniel. "Consumer-resource interactions and biological invasions : insights from an invasive Ponto-Caspian study system." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680885.
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This study attempts to understand some aspects of ecological invasions from the perspective of consumer-resource interactions. Two successful Ponto-Caspian invaders of Irish lacustrine habitats, Hemimysis anomala and Chelicorophium curvispinum, are considered here. I establish that the invasive H. anomala has a higher per capita functional response towards cladoceran prey than does a native analogue, Mysis salemaai, whether consumption occurs alone, in conspecific groups, or in conspecific groups in the presence of a higher fish predator. In addition, the presence of this higher predator reduces the consumption of cladocerans by the natives, but not by the invaders. In situ experiments designed to track the vertical migrations of both mysids further reveal that the functional response of the invader is both higher and. more variable over diurnal periods than that of the native. Thus, the impacts of invaders - or natives - on prey can depend on per capita effects, how these vary spatiotemporally and modulation by con specifics and predators. Where invaders are potential resources for native species, as is the case with C. curvispinum, I demonstrate how two defensive characteristics - the propensity to construct protective tubes and to associate with complex habitat architecture - can systematically dampen interactions with a range of vertebrate and invertebrate predators. I highlight how associating with habitat architecture collapses predator capture rates across body mass distributions and, using artificial manipulations of habitat architecture, I demonstrate how increases in the availability of predator-free space can reduce the magnitude and alter the shape of predatory functional responses. These findings allude to the importance of defensive characteristics in mediating the persistence of C. curvispinum. Altogether, this work demonstrates: (i) the utility of functional responses as impact assessment tools; (ii) the importance of quantifying both top-down and bottom-up contributions to interactions; and (iii) the need to consider the context in which interactions occur.
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Pujol, Buxó Eudald. "Biological invasions: a temporal, spatial and plastic point of view: the case of Discoglossus pictus in Europe = Invasions biològiques: un punt de vista temporal, espaial i plàstic : el cas de Discoglossus pictus a Europa." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/456898.
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The rates at which allochthonous species are introduced and become invasive worldwide are unprecedented and accordingly, the number of studies on invasion biology have increased during the past years. However, biological invasions are still seemingly underused as natural laboratories to test essential biological theory. In this sense, the nine studies – ordered in three parts, which function as thematic blocks – presented in this thesis try to globally give an evolutionary – apart from ecologic – point of view on the ongoing invasion of the Mediterranean Painted Frog (Discoglossus pictus) in Europe. This frog is native to Northern Africa and was introduced from Algeria in Southern France approximately a century ago, being nowadays present on a wide coastal strip of approximately 250km in SE France and NE Spain, constantly colonizing new areas.
The aim of “PART A: Intraspecific variation along the invasive range of Discoglossus pictus” is the examination at a phenotypic and genomic level of possible differences across populations within the invasive range of the species. We observe that the Mediterranean Painted Frog is not a uniform unit in its invasive range in Europe: mean size of adults and life-history traits related to mean annual precipitation, while substantial genetic differences among populations are most probably created by the expansion history itself.
The aim of “PART B: Intraguild competition in tadpoles of Discoglossus pictus” is to study and discuss the role of Discoglossus pictus tadpoles as potential competitors for the larvae of native anurans. We here see that the Mediterranean Painted Frog represents, physiologically, a unique addition to the local tadpole guild, characterized by a very rapid and consumption-oriented growth, and that these tadpoles are able to increase the quality and quantity of its food intake when these possibilities are provided. This poses these tadpoles as potentially very disruptive of the natural dynamics of native anurans. Concerning the competitive relationship between the Natterjack Toad (Epidalea calamita) and the Mediterranean Painted Frog, we can observe that it changes according to previous evolutionary history of populations. In this sense, populations of the native toad that have had a greater number of generations of contact with the invasive frog are able to inflict a greater competitive distress on the invasive tadpoles. Both competitors also differ mildly in their breeding preferences, but nevertheless, both species seem forced to end up competing very often at a pond level. Within ponds, the trophic position of both species can respond either to evolutionary or to ecological patterns with the data gathered hitherto.
Finally, in “PART C: Tadpoles of Discoglossus pictus as prey for aquatic native predators”, two studies examine if invasive tadpoles modify its phenotypes in front of an array of – native and invasive – predators, testing also the effectiveness of the possible changes. Interestingly, the invasive frog presents a pattern of inducible defences which would be expected for a native anuran, responding to all native predators effectively, while lacking responses in front of introduced or invasive predators.
Globally, the complex evolutionary history of the local anuran assemblages poses the Mediterranean Painted Frog as a good model for ecological and evolutionary studies reaching beyond invasion biology, as it is very particular case of invasive species, in which effects of previous recurrent shared evolutionary history with similar competitor / predator species are probably present.Les invasions biològiques estan essent aparentment infrautilitzades com a laboratoris naturals per investigar certs aspectes teòrics fonamentals de la biologia. En aquest sentit, els nou estudis presentats en aquesta tesi – ordenats en tres blocs temàtics – intenten donar un punt de vista evolutiu – a part d'ecològic – sobre la invasió de la granota pintada (Discoglossus pictus) a Europa. Aquesta granota es va introduir des d'Algèria a Banyuls de la Marenda (Catalunya Nord) fa aproximadament un segle, arribant ara des de Montpeller fins a Sant Celoni, colonitzant contínuament noves àrees. A la "PART A: variabilitat intraespecífica al llarg de la distribució invasora de Discoglossus pictus" observem que la granota pintada no forma un conjunt uniforme de poblacions en la seva distribució invasora europea, ni fenotípica ni genòmicament: la mida i els trets de la història vital dels adults es relacionen amb la precipitació mitjana de cada zona, mentre que la diferenciació genètica entre poblacions ha estat molt probablement creada pel procés d'expansió en sí. A la "PART B: Competència intra-gremi en capgrossos de Discoglossus pictus" veiem que la granota pintada representa, fisiològicament, una addició única al gremi local de capgrossos, caracteritzada per un creixement molt ràpid i orientat al consum, amb bones capacitats d'augmentar la qualitat i quantitat de la ingesta d'aliments quan n'hi ha possibilitats. Pel que fa a la freqüent relació de competència entre Epidalea calamita i Discoglossus pictus, podem observar que els capgrossos autòctons que han tingut un major nombre de generacions de contacte amb els invasors són capaços d'infligir un major estrès competitiu en aquests. Els dos competidors també difereixen lleugerament en les seves preferències de cria, però semblen estar obligats a acabar competint molt sovint a nivell de bassa. Dins d'aquestes, la posició tròfica d'ambdues espècies pot respondre tant a patrons evolutius com a patrons ecològics amb les dades recollides fins ara. Finalment, a la "Part C: Capgrossos de Discoglossus pictus com a presa per depredadors aquàtics autòctons" veiem que la granota invasora presenta un patró de defenses induïbles que s'emmotlla al que s'esperaria per a un anur autòcton, responent a tots els depredadors nadius eficaçment, mancant respostes davant de depredadors introduïts. La complexa història evolutiva dels conjunts d'anurs del mediterrani occidental posa la granota pintada com un cas molt particular d'espècie invasora, on no ses poden descartar els efectes d'una història co-evolutiva prèvia entre espècies similars.
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Crider, Kimberly Kay. "BIOLOGICAL CONTROL: EFFECTS OF TYRIA JACOBAEAE ON THE POPULATION DYNAMICS OF SENECIO JACOBAEA IN NORTHWEST MONTANA." The University of Montana, 2010. http://etd.lib.umt.edu/theses/available/etd-03092010-140634/.
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Biological control, using introduced, specialist insects is a common strategy for controlling plant invasions. However, the efficacy of biological control agents in controlling their host plants is rarely quantified population level. I quantified the impact of a specialist biological control agent, the cinnabar moth (Tyria jacobaeae) on its host plant, tansy ragwort (Senecio jacobaea) in northwest Montana. Cinnabar moth damage and its effects on important plant vital rates were tested with and without specialist herbivores. The presence of moth larvae corresponded to a reduction in population growth rates to less than one, compared to herbivore-free controls, indicating the potential for successful biological control by this insect. However, delayed effects of cinnabar moth herbivory on tansy ragwort vital rates were realized during the year following moth herbivory, after the moths had disappeared from the system. Individual damage to flowering plants in 2005 led to increased survival of these plants in the following year compared to controls, by reverting back to a vegetative state. In addition, seed set was reduced in plants that were damaged as juvenile rosettes in 2005 that went on to flower in 2006. When these delayed effects were combined in matrix models, gains in adult survival did not outweigh the decreases in fecundity or transition rates in terms of population growth and our initial conclusions remained unchanged. However, further study revealed that moth larvae were more likely to be depredated by carpenter ants in xeric sites suggesting that moth populations may not be sustained in these areas. Cinnabar moth larvae can be effective in this system provided they consume a large number of seeds (>90%) in consecutive years, but requires that moth populations are established and sustained from year to year. While herbivores do show the ability to control an invasive plant species, this relationship is strongly contextual in this system. This work emphasizes the importance of recognizing the influence of habitat context on the outcome plant-herbivore interactions, specifically in invaded ecosystems.
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Seyed, Sadr Mohamad. "SLIT proteins inhibit malignant brain tumour cell invasion via downregulation of pro-invasive genes." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110340.
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Most cancer deaths result from the progression of the tumour pathology whereby a localised mass evolves into an invasive and metastatic disease, spreading away from the main tumour mass. Malignant brain tumours such as glioblastoma and medulloblastoma are among the most invasive human cancers. The Slit-Robo pathway is extensively characterised as a repellent of axons and neural cells. Therefore we hypothesised that Slit proteins would repel invasive brain tumour cells. The first chapter of this thesis provides a thorough introduction of the oncology field as it pertains to malignant brain tumour biology and to the field of Slit-Robo family of proteins. The second chapter provides evidence for Slit proteins and their inhibitory effect on malignant brain tumour cell invasion. We further characterise the signaling pathway employed by Slit proteins to impart an inhibitory effect on tumour cell invasion. We present data suggesting that Slit proteins decrease the transcriptional expression of numerous pro-invasive and pro-angiogenic genes in malignant brain tumour cells. We characterise the product of one of these genes, MMP14, as a protease of Robo proteins. A model is proposed that explains the observation that decreasing the expression of MMP14 leads to a decrease in brain tumour cell invasion. These results suggest that malignant brain tumour cells respond to Slit by modulating a series of transcripts critical for cell invasion. Therefore, targeting malignant brain tumour cells with Slit proteins or chemical analogues that mimic Slit's effects may provide a potentially novel anti-invasive therapy.La transformation d'une tumeur primaire en tumeur maligne et métastatique, s'éloignant du point d'origine, est souvent la principale cause de décès chez le patient. Les tumeurs cérébrales malignes tel les glioblastomes et les médulloblastomes sont parmi les plus invasives cancers humains. La voie de signalisation de Slit-Robo a été largement caractérisée et montre l'implication de Slit-Robo dans la répulsion des axones et cellules neuronales. Dans cette étude, nous avons étudié la possibilité que Slit-Robo pourraient repousser les cellules cancéreuses invasives cérébrales. Le premier chapitre de cette thèse présente une introduction approfondie du rôle de la famille des protéines Slit-Robo dans le contexte du cancer et de la biologie des tumeurs cérébrales. Le deuxième chapitre présente des preuves de l'implication des protéines Slit et leur rôle dans l'inhibition de l'invasion des cellules de tumeurs cérébrales. Aussi, la caractérisation de la voie de signalisation employée par les protéines Slit dans l'inhibitionde l'invasion des cellules cancéreuses a été montrée. De plus, cette étude présente des résultats qui suggèrent que les protéines Slit diminuent l'expression de la transcription degènes pro-angiogénique et pro-invasif des cellules tumorales. Nous avons aussi identifié MMP14 comme une protéase des protéines Robo et dont l'expression est influencée par les protéines Slit. Finalement, nous proposons un modèle démontrant qu'une diminution de l'expression de MMP14 induit une réduction de l'invasion des cellules tumorales du cerveau.
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Robinson, Todd Peter. "Application of advanced techniques for the remote detection, modelling and spatial analysis of mesquite (prosopis spp.) invasion in Western Australia." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/620.
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Invasive plants pose serious threats to economic, social and environmental interests throughout the world. Developing strategies for their management requires a range of information that is often impractical to collect from ground based surveys. In other cases, such as retrospective analyses of historical invasion rates and patterns, data is rarely, if ever, available from such surveys. Instead, historical archives of remotely sensed imagery provides one of the only existing records, and are used in this research to determine invasion rates and reconstruct invasion patterns of a ca 70 year old exotic mesquite population (Leguminoseae: Prosopis spp.) in the Pilbara Region of Western Australia, thereby helping to identify ways to reduce spread and infill. A model was then developed using this, and other, information to predict which parts of the Pilbara are most a risk. This information can assist in identifying areas requiring the most vigilant intervention and pre-emptive measures. Precise information of the location and areal extent of an invasive species is also crucial for land managers and policy makers for crafting management strategies aimed at control, confinement or eradication of some or all of the population. Therefore, the third component of this research was to develop and test high spectral and spatial resolution airborne imagery as a potential monitoring tool for tracking changes at various intervals and quantifying the effectiveness of management strategies adopted. To this end, high spatial resolution digital multispectral imagery (4 channels, 1 m spatial resolution) and hyperspectral imagery (126 channels, 3 m spatial resolution) was acquired and compared for its potential for distinguishing mesquite from coexisting species and land covers.These three modules of research are summarised hereafter. To examine the rates and patterns of mesquite invasion through space and time, canopies were extracted from a temporal series of panchromatic aerial photography over an area of 450 ha using unsupervised classification. Non-mesquite trees and shrubs were not discernible from mesquite using this imagery (or technique) and so were masked out using an image acquired prior to invasion. The accuracy of the mesquite extractions were corroborated in the field and found to be high (R2 = 0.98, P<0.001); however, accuracy varied between classes (R2 = 0.55 to 0.95). Additional sampling may be required in some of the wider class intervals, particularly the moderate density class (30 to 90%) as sampling frequency was poor within the range of 60 to 90%. This is a direct result of there being relatively few quadrats available to be randomly selected in this class. That is, quadrats with between 60-90% cover were only evident in 4% of the test area. A more robust approach would, therefore, be to split this class into two (e.g. 30-60% and 60-90%) and select an additional 15 quadrats in the 60-90% range. The resolution of the imagery (1.4 m) precluded mapping shrubs smaller than 3 m2. Rates and patterns were compared to mesquite invasions in its native range.It was determined that: (i) the shift from grass to mesquite domination had been rapid, with rates of increase in canopy cover comparable to invasive populations where it is native; (ii) rate of patch recruitment was high in all land types (stony flats, red-loamy soils and the riparian zone), but patch expansion and coalescence primarily occurred over the riparian zone and redloamy soils; (iii) mesquite had been spread by sheep and macropods and the recent switch to cattle is likely to exacerbate spread as it is a far more effective dispersal vector; and (iv) early successional patterns, such as high patch initiation followed by coalescence of existing stands are similar to where mesquite is native, but patch mortality did not occur. A knowledge based model was used to predict which parts of the Pilbara region are most at risk. Several limitations of models often employed in predicting suitability ranges of invasive plants were identified and include: (i) an inability to incorporate the notion that within a suitability range there is likely to be a scale of favourability; (ii) an inability to assign greater importance to evidence that is likely to have more importance in defining the areas suitable for invasion; and (iii) an inability to control the level of conservatism in the final results. These three shortcomings were mitigated through the use of: (i) fuzzy membership functions to derive a range of favourability from poor to best; (ii) pairwise comparison to derive higher weights for layers perceived to be more important and vice versa; and (iii) the use of ordered weighted averaging to directly control the level of conservatism (or risk) inherent in the models produced.Based on the outcomes of the historical reconstruction of spatial rates and patterns, data sources included land types, land use, and the derivation of a steady state wetness index from spot height data. Model outputs were evaluated using two methods: the area under the curves (AUC) produced from relative operating characteristic (ROC) plots and by the maximum Kappa procedure. Both techniques agreed that the model most representative of the validation data was the one assuming the most risk. To create a Boolean output representing areas suitable/not suitable for invasion, optimal cut-points were derived using the point closest to the top left hand corner of the ROC plot and by the maximum Kappa method. Both methods obtained identical cut-points, but it is argued that the coefficient produced by the maximum Kappa method is more easily interpreted. The highest AUC was found to be 0.87 and, based on the maximum Kappa method, can be described as good to very good agreement with the validation records used. Digital multispectral imagery (DMSI), acquired in the visible and near infrared portions of the spectrum (3 visible bands, 1 near infrared) with a spatial resolution of 1 m and hyperspectral imagery (126 bands, 3 m spatial resolution) was acquired to assess the potential of developing a reliable and repeatable mapping tool to facilitate the monitoring of spread and the effects of control efforts. Woody vegetation was extracted from the images using unsupervised classification and grouped into patches based on contiguity. Various statistics (e.g. maximum, minimum, median, mean, standard deviation, majority and variety) were assigned to these patches to garner more information for species separation.These statistics were explored for their ability to separate mesquite from coexisting species using Tukey’s Honestly Significantly Different (HSD) test and, to reduce redundancy, followed by linear discriminant analysis. Two approaches were taken to select the patch statistics offering the best discrimination. The first approach selected patch statistics that best discriminated all species (named “overall separation”). This was compared to a second approach, which selected the best patch statistics that separated each species from mesquite on a pairwise basis (named “pairwise separation”). The statistics offering the best discrimination were used as input in an Artificial Neural Network (ANN) to assign class labels. An incremental cover evaluation, whereby producer’s accuracy was computed from mesquite patches grouped into various size-classes, showed that identification of mesquite patches smaller than 36 m2 was relatively low (43-51%) regardless of the method used for choosing between the patch statistics or image type. Accuracy improved for patches >36 m2 (66-94%) with both approaches and image types. However, both approaches used on the hyperspectral imagery were more reliable at capturing patches >36 m2 than the DMSI using either approach. The lowest omission and commission rates were obtained using pairwise separation on the hyperspectral imagery, which was significantly more accurate than DMSI using an overall separation approach (Z=2.78, P<0.05), but no significant differences were found between pairwise separation used on either media.Consequently, all methods and imagery types, except for DMSI processed using overall separation, are capable of accurately mapping mesquite patches >36 m2. However, hyperspectral imagery processed using pairwise separation appears to be superior, even though not statistically different to hyperspectral imagery processed using overall separation or DMSI processed using pairwise separation at the 95% confidence level. Mapping smaller patches may require the use of very high spatial resolution imagery, such as that achievable from unmanned airborne vehicles, coupled with a hyperspectral instrument. Alternatively, management may continue to rely on visual airborne surveys flown at low altitude and speed, which have proven to be capable at mapping small and isolated mesquite shrubs in the study area used in this research.
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Lesieur, Vincent. "Invasion de la punaise américaine Leptoglossus occidentalis en Europe : une contribution à la compréhension des invasions fulgurantes." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2045/document.
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Les dernières décennies représentent un tournant majeur concernant les invasions biologiques avec une augmentation sans précédent de leur rythme et de leur ampleur, en lien direct avec les activités humaines, en particulier la mondialisation. Certains invasifs se propagent à une vitesse très rapide dans leur nouveau milieu. L’invasion européenne de la punaise Leptoglossus occidentalis, illustre parfaitement ce phénomène et offre un modèle d’étude particulièrement intéressant. Cette thèse a pour but de tester des hypothèses permettant d’expliquer la rapidité de cette invasion. Pour répondre à cet objectif, nous avons choisi d’utiliser une approche pluridisciplinaire combinant des études de génétique des populations (natives et introduites) à des études de biologie et d’écologie des populations invasives. Grâce à l’utilisation de marqueurs moléculaires et de méthodes Bayésiennes (ABC), nous démontrons que l’invasion en Europe suit un scénario " tête de pont ", au sens où la population invasive de l’Est de l’Amérique du Nord a servi de source pour l’invasion européenne. Nos résultats confirment les soupçons d’introductions multiples dans des zones géographiquement déconnectées. En outre, l’étude de génétique des populations, associée aux mesures expérimentales des capacités de vol, indique que les capacités intrinsèques de dispersion de cette espèce sont particulièrement élevées. Les conditions rencontrées en Europe par les populations introduites ne sont pas un frein à l’invasion. L’espèce s’accommode parfaitement des nouvelles essences de conifères rencontrées sur le continent. La polyphagie observée dans la zone native est confirmée dans la zone d’introduction européenne, constituant un atout pour l’établissement des populations. De plus, cette étude révèle les risques écologiques que cette espèce représente pour la flore native européenne. Les dégâts occasionnés semblent s’additionner à ceux des ravageurs natifs, diminuant ainsi le potentiel de régénération naturelle. L’ensemble de ces résultats constitue une contribution à la connaissance des mécanismes sous-tendant les invasions biologiques, notamment sur la rapidité de propagation de certains invasifs, et met l’accent sur des phénomènes sous-estimés il y a encore peu de temps comme le scénario d’invasion " tête de pont "During the last decades, biological invasions were observed to increase exponentially, at an unprecedented rate and magnitude, in direct relation with the human activities, especially globalization. In this context, some invasive species spread very quickly in the area of introduction. The European invasion of Leptoglossus occidentalis is a good example of this phenomenon. This study aimed at testing some hypotheses to explain the rapidity of this invasion. To reach this goal, we used a multidisciplinary approach combining population genetics (analyzing samples from native and invaded areas) with a study of biological and ecological characteristics of the invasive populations. Through the use of molecular markers and Bayesian methods (ABC), we confirmed previous suspicions and demonstrated that the European invasion proceeded from multiple introductions in distant geographic areas. Our results also indicated that a primarily invaded area of Eastern North America acted as a bridgehead for the invasion in Europe. Moreover, population genetics, combined with an experimental measurement of the bug flight capabilities using flight mills, revealed that the intrinsic capacities of dispersion of this species are particularly high. The environmental conditions of the newly invaded areas in Europe did not constitute a barrier to the invasion of L. occidentalis. Its high degree of polyphagy was confirmed on European conifers, quite all species being susceptible to be exploited, thus favoring population establishment. . Furthermore, this study highlights the ecological threat represented by this insect which can affect the native flora in Europe. Actually, bug damage which can be important, seems to be additive to those of native insects exploiting cone and seed resources, thus decreasing the potential of natural regeneration. This work contributes to improve knowledge on biological invasions, especially to understand the reasons underlying the rapid spread observed in some invasive species, and highlights phenomenon underestimated until recently such as the Bridgehead scenario
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Allen, Victoria. "Uncovering Pathways Regulating ILC Metastasis Through miRNA Expression Analysis and Generation of Novel Invasive ILC Models." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39616.
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Invasive lobular carcinoma (ILC) is the second most common form of breast cancer. ILC presents at later stages with many challenges, therefore improved diagnostic and therapeutic targets are needed. A microRNA (miRNA) genome analysis identified miR-23c and miR-23b-3p as possible regulators of ILC invasion due to their significantly increased expression in invasive compared to minimally invasive ILC cell lines. By decreasing the levels of miR-23c and miR-23b-3p using hairpin inhibitors, the invasive MDA-MB-330 cell line had significantly reduced invasion, while overexpressing these miRNAs using mimics in the minimally invasive MDA-MB-134VI cell line increased invasion. During the course of this study, it became apparent that limited tools exist for studying invasive ILC. Therefore, two more invasive ILC cell line models were created by isolating and expanding MDA-MB-134VI cells that had invaded through Matrigel® coated invasion chambers. This thesis has thus created new models of invasive ILC as well as identified miR-23c and miR-23b-3p as regulators of MDA-MB-330 and MDA-MB-134VI cell line invasion.
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Donaldson, Jason Ernest. "The invasion ecology of Acacia elata (A. Cunn. Ex Benth.) with implications for the management of ornamental wattles." Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85808.
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Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: This thesis explores how human dictated methods of introduction and species-specific traits interact to define spatial patterns in invasive plant populations using Acacia elata as a model species. I initially asked whether the relatively small invasive extent (when compared to congeners introduced for forestry or dune stabilization) of a species used widely for ornamental purposes (A. elata) is due to low rates of reproduction in South Africa. Results indicate that A. elata has similar traits to other invasive Australia Acacia species: annual seed input into the leaf litter was high (up to 5000 seeds m-2); large seedbanks develop (>20 000 seeds m-2) in established stands; seed germinability is very high (>90%); seeds accumulate mostly in the top soil layers but can infiltrate to depths of 40cm; and seed germination appears to be stimulated by fire. I argue that the current limited distribution of invasive A. elata populations is not attributable to species-specific reproductive traits. Following on from this I addressed the relative importance of species traits, the recipient environment, and introduction dynamics using species distribution models and spread models defined using a range of parameters representative of invasive Australian acacia species. Results indicate that in the early stages of simulated invasions, the number of trees introduced was the most important parameter influencing abundance and extent, while the placement of introduction foci in urban areas associated with ornamental introductions limited the extent and abundance of invasive populations. I suggest that conditions relating to human-mediated introduction events initially mask the influence of intrinsic species traits and help to explain the failure and success of species associated with specific human-shaped pathways. Third, I used scale-area curves to determine how these human-dictated introduction conditions influenced the spatial structure of populations. The fractal dimension (Dij) of A. elata populations indicates plot scale (2.5-25m) spread with high densities that are increasing. Artefacts of introduction history were observed at the regional scale (2.5-25km) - populations are contiguous around introduction foci such as towns and roads. Moreover, fragmentation of A. elata populations at local to landscape scales (0.25-2.5km) is due to a combination of the haphazard regional placement and limited secondary dispersal vectors, both of which can be linked to their introduction history. In summary, this study used a combination of field-based data, modelling techniques and broad-scale sampling methods to assess how intrinsic species traits and introduction conditions mediate invasive spread. I conclude that introduction history can have a long-lasting (100+ years) influence on the spatial structure and distribution of invasive plants, which can mask the influence of individual species traits.
AFRIKAANSE OPSOMMING: Alhoewel menigte plant spesies deur mense ingevoer word, word slegs 'n klein hoeveelheid van plante indringers. Die beperkte aantal spesies wat in nuwe habitatte vestig en versprei, kan grotendeels toegeskryf word aan die omgewing en mensgemaakte hindernisse ten opsigte van oorlewing, voortplanting en verspreiding. In hierdie tesis gebruik ek Acacia elata as ʼn model spesie om te ondersoek hoe die invoeringsproses sowel as spesie spesifieke eienskappe die ruimtelike struktuur van indringende populasies bepaal. Aanvanklik was my vraag of die relatiewe klein indringingsarea van ʼn spesie wat ingevoer is vir ornamentele doeleindes (Acacia elata), teenoor die groot indringingsareas van Australiese Acacia-spesies wat ingevoer is vir bosbou of duin stabilisering, die gevolg is van lae voortplantings tempo in Suid-Afrika. Resultate dui daarop dat A. elata soortgelyke eienskappe as ander indringende Australië akasia spesies het: jaarlikse saad produksie is hoog (tot 5000 sade m - 2); groot ontwikkelde saadbanke (> 20 000 sade m - 2); hoë saad ontkieming (> 90 %); saad versamel in die boonste grondlae, alhoewel dit kan infiltreer tot 'n diepte van 40 cm; laastens, ontkieming word deur vuur gestimuleer. Hierdie resultate stel voor dat die huidige beperkte verspreiding van indringende A. elata populasies nie die gevolg is van spesie spesifieke voortplantings eienskappe nie. Gevolglik het ek 11 indringende Australiese akasia-spesies ondersoek om die relatiewe belangrikheid van spesie eienskappe, die area waar hul geplant is, asook invoerings aspekte te ondersoek. Resultate wys dat die aantal bome wat ingevoer is, die belangrikste eienskap was ten opsigte van digtheid en verspreiding van ʼn indringende spesie, terwyl invoering naby fokuspunte in stedelike gebiede weer spesie digtheid en verspreiding beperk. Hierdie resultate toon dat spesies eienskappe aanvanklik nie ʼn groot invloed het op hul sukses nie, maar dat hul sukses eerder afhang van waar hul geplant word. Derdens, gebruik ek skaal - area kurwes om te bepaal hoe die invoering van A. elata die ruimtelike struktuur van populasies beïnvloed het. Die fraktale dimensie (Dij) van A. elata bevolkings dui op verspreiding by die plaaslike vlak (2,5 - 25m), wat voorstel dat verspreiding nie op hierdie skaal beperk is nie. Eienskappe van die rede/metode van invoering was wel waargeneem op die groter skaal (2.5 - 25km) waar populasies digter was naby dorpe en paaie. Die intermediêre skaal (0,25 - 2.5km) dui daarop dat A. elata populasies huidiglik beperk word deur 'n kombinasie van lukrake plasing en beperkte sekondêre verspreiding, albei wat gekoppel kan word aan hul invoer geskiedenis. Hierdie studie maak dus gebruik van 'n kombinasie van veld gebaseerde data, modellerings tegnieke en breë skaal steekproefmetodes om te evalueer hoe algemene spesies eienskappe en invoer toestande verspreiding bepaal. Sodoende verskaf ek ʼn raamwerk om die invloed van invoer toestande op die ruimtelike struktuur en verspreiding van ornamentele plant indringers te verstaan.
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Boubou, Angham. "Apport de l'approche évolutive pour l'étude de l'invasion de l'acarien rouge de la tomate, Tetranychus evansi." Thesis, Montpellier, SupAgro, 2010. http://www.theses.fr/2010NSAM0018.
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L'acarien rouge de la tomate Tetranychus evansi (Tetranychidae) est considéré comme une espèce invasive à fort impact économique sur les cultures de solanacées. Il a été découvert pour la première fois en 1954 au Brésil, d'où il est probablement originaire. Historiquement, T. evansi a d'abord été signalé en Afrique et plus récemment en Europe et en Asie. L'objectif de cette thèse était de reconstruire les routes de colonisation de T. evansi et de dégager le scénario évolutif décrivant le mieux l'histoire de l'invasion. Nous avons d'abord analysé des échantillons collectés dans son aire actuelle de distribution, à l'aide des séquences d'un fragment du gène codant pour la sous-unité I de la Cytochrome Oxydase (COI) de l'ADN mitochondrial et de la région ITS1-5,8S-ITS2 de l'ADN nucléaire ribosomique. Les données soutiennent l'hypothèse d'une origine sud américaine de cette espèce et ont révélé que des événements d'invasions multiples et cryptiques ont eu lieu lors de la colonisation de l'Europe. L'invasion résulte de deux lignées génétiquement divergentes et originaires de deux régions géographiques distantes au Brésil. Ces deux lignées semblent avoir des potentiels invasifs contrastés. Elles s'hybrident au laboratoire ainsi que dans la nature. Grâce à 16 locus microsatellites que nous avons développés et utilisés comme marqueurs, nous avons déterminé les zones géographiques de cette hybridation. Nous avons également pu estimer des paramètres historiques de l'invasion et confronter différents scénarios d'introduction, par la comparaison de la composition génétique des populations récemment introduites avec celles de l'aire d'origine de T evansi, et par l'utilisation de la méthode d'inférence bayésienne (Approximate Bayesian Computation, ABC). Les résultats ABC contredisent partiellement le scénario d'invasion basé uniquement sur des données historiques. Ils suggèrent que T. evansi serait d'abord arrivé en Europe dans le sud de l'Espagne (en Andalousie) bien avant les signalements historiques. Ainsi, l'Andalousie semble avoir servi de source de colonisation pour des nouvelles zones en Afrique, d'autres régions méditerranéennes et d'Asie. Les résultats de cette thèse ouvrent des perspectives d'étude visant à comprendre pourquoi certaines populations d'une espèce allochtone réussissent à s'établir et à envahir un nouvel écosystèmeThe red tomato spider mite Tetranychus evansi (Tetranychidae) is regarded as an invasive species having an important economic impact on solanaceous crops. It was first discovered in Brazil in 1954, where it probably originated. Based on historical records, T. evansi was first reported in Africa and more recently in Europe and Asia. This work aims at reconstructing the colonization routes of T. evansi and identifies the scenario that best describes the evolutionary history of the invasion. To do this, we first analyzed samples collected from most parts of the world where the mite is currently known to occur. We used sequence variation of a fragment of the mitochondrial Cytochrome Oxidase I (COI) sub-unit I gene and the ITS1-5.8S-ITS2 of the nuclear ribosomal DNA. Our results were consistent with the hypothesis of a South American origin of this species. They also suggested that the invasion of south Europe resulted from multiple cryptic introductions from two genetically divergent lineages originated from two distant geographical regions in Brazil. These two lineages seem to have a differential invasive potential. Despite the high genetic divergence, crosses between mites stemming from the two lineages do occur both in the laboratory and in nature. Second, we used 16 microsatellite loci that we developed for this study and in association with Approximate Bayesian Computation (ABC) methods; we reconstructed the historical events of the cryptic invasion of the pest. ABC results challenge the invasion scenario captured by historical data only. They suggest that T. evansi first arrived to Europe in Southern Spain (Andalusia) long before historic records. Thus, Andalusia seems to have served as a source for colonization of new areas in Africa and other Mediterranean regions. The results obtained in this thesis provide an interesting framework to further study and understand why some populations of an exotic species might become invasive
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Selge, Sebastian. "Public and scientific discourses on biological invasions : social representations of invasive non-native species in Scotland." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=183833.
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Invasive non-native species are believed to be one of the biggest threats to biodiversity. Until now biological invasions have been mainly studied from a biological perspective and much research has been undertaken to investigate species’ ecology and potential options for management. Comparatively little attention has been devoted to questions regarding the social construction of the issue. This is despite invasion biologists increasingly acknowledging the fundamental importance of human perceptions, beliefs, attitudes and values inherent in debates about invasive non-native species. This thesis employs a mix of methods from the social sciences to investigate the social construction of biological invasions. Research conducted here is based on the theory of social representations. Thus, taking a social scientific perspective, the thesis contributes to both the development of the theory and an identification of beliefs inherent in the debate on biological invasions and their relationship to people’s attitudes towards species and their management. Those species attributes that predominantly shape the debate – but yet appear to be under-researched – are identified. Based on the findings in this thesis I argue that invasion biology would benefit from a more explicit and transparent use of its concepts and terminology. This will have implications also for the communication with policy makers, conservation managers and the general public. Recommendations for future research are discussed along with limitations of the thesis.
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Camacho-Cervantes, Morelia. "Heterospecific social interactions of the invasive guppy (Poecilia reticulata) : a potential trait to enhance invasion success." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6561.
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From all the species that arrive to a novel environment, very few manage to form a viable population. The guppy, a very successful invader, is a highly social species that performs some of its vital tasks (e.g., foraging, avoiding predators) in groups. This thesis aimed to quantify heterospecific association benefits that enhance invasion success. Interactions between invaders and natives could be one of the environmental characteristics of a place that increase its risk of invasion. I evaluated the tendency of an invasive species to associate with native individuals with similar ecological requirements. I tested the hypothesis that invaders gain exploring, acquisition of information and foraging benefits when socializing with natives. In these experiments I used the guppy as the invasive model species and endangered native Mexican topminnows (Poeciliopsis infans, Skiffia bilineata, Ameca splendens, Zoogoneticus tequila, Xenotoca eiseni and Girardinichthys viviparous). I found that guppies shoal with other species in Trinidad (Poecilia picta and Poecilia sphenops), where they are native (Chapter 2) and that this trait remains when they are invasive (Chapter 3). Guppies are equally willing to explore novel environments when accompanied by heterospecifics or conspecifics. Guppies are more willing to explore complex environments than simple ones. Moreover, when exploring simple environments they have a higher association tendency, regardless of the partner' species (Chapter 4), which could lead them to acquire the benefits of grouping behaviour and avoid Allee effects - the disadvantages of being part of a small group. In the contexts in which they were tested guppies gained as much information by associating with heterospecifics as with conspecifics (Chapter 5). Finally, I found that when shoaling in bigger shoals guppies are able to locate food faster and spent more time foraging. The benefits of increased shoal size were maintained when the additional guppies were replaced with heterospecifics. However, they derive more benefits from the species they are more willing to associate with (Chapter 6). These results uncover a mechanism enabling founding individuals to survive during the most vulnerable phase of an invasion and help explain why guppies have established viable populations in many parts of Mexico as well as in every continent except Antarctica.
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Riley, Leslie Anne. "Estimating invasive species impact interaction strengths, abundance and the role of productivity in a freshwater invasion /." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Dissertations/Fall2008/l_riley_111808.pdf.
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Berry, Katharine M. "The role of parasites in the invasion ecology of Harmonia axyridis." Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/27336.
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The success of an invasive alien species is often attributed to the ecological advantage gained from natural enemy release. Numerous factors have been suggested as contributing to the success of Harmonia axyridis as an invasive alien species, including enemy release. This thesis studied the interactions of several parasites with H. axyridis, investigating parasite transmission, growth and virulence as well as host immune responses, thereby shedding light on the potential role of enemy release in the invasion biology of this ladybird. Benefits gained by invasive alien species from enemy release diminish if parasites of native species shift hosts to exploit the novel invader. The fungal ectoparasite Hesperomyces virescens began infecting H. axyridis shortly after it invaded the UK, probably as a result of a host shift from Adalia bipunctata. This study found a rapid increase in H. virescens prevalence over three years in London H. axyridis populations. Laboratory study showed H. virescens transmission and growth to be more efficient on A. bipunctata than the novel host. In addition, reciprocal interspecific transfers of H. virescens strains isolated from A. bipunctata and H. axyridis revealed that the infection characteristics of the fungi from these two hosts differed, suggesting strains may have diverged after the initial shift from A. bipunctata to better exploit the host from which they were derived. Laboulbenialian fungi were previously thought to have negligible impacts on host fitness. A detailed examination of H. virescens infecting H. axyridis found distinct virulence, with infections resulting in a 50% reduction in host lifespan. In addition, chronic H. virescens infection in males caused acceleration in the age-associated decline in body condition while for females, infection triggered fecundity senescence and a faster age-related decline in fertility. While their role in accelerating ageing is debated, the results presented here provide evidence that infectious diseases can drive the ageing process in this insect species. In nature, multiple parasites affecting a single host are common. The effect of co-infection on the virulence caused by two fungal infections was characterised using H. axyridis and A. bipunctata hosts. The ability of two ladybird species to defend against an acute fungal parasite, while infected with the relatively avirulent H. virescens was found to be sex-specific. While for females, the presence of co-infection did not alter the virulence seen in singly infected females, a higher mortality rate existed for co-infected males compared with those infected singly. Previously, H. virescens has been considered to be avirulent, however, this study provides evidence that this chronic fungal parasite may be important when considering the mortality associated with co-infections in the field. The invasive success of H. axyridis has, in part, been attributed to a more vigorous immune ability compared with other competitor species. Previously, field studies have shown that the prevalence of the parasitoid wasp Dinocampus coccinellae in H. axyridis is considerably lower than in the UK primary host of this wasp, Coccinella septempunctata. The extent to which the prevalence asymmetry in the field is driven by differences in host encapsulation response was tested by first comparing the encapsulation ability of C. septempunctata and H. axyridis directed against an artificial implant. Following this, the encapsulation response of D. coccinellae parasitized individuals was assessed and compared between the two host species. While encapsulation ability did not differ between the host species, and D. coccinellae did not affect the immune response of H. axyridis, wasp parasitism did alter the encapsulation ability of C. septempunctata, although it was inconsistent across sexes and populations. Overall, this thesis furthers our understanding of the fungal parasite H. virescens and its association with the notorious invader H. axyridis. The research presented here also demonstrates the use of H. axyridis as a model system in areas other than invasion ecology and furthermore, contributes to understanding the role of infectious disease in the rate of ageing. Finally, sex-specific effects were found across the chapters of this thesis, demonstrating the use of H. axyridis in the study of sex-specific effects of infections.
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Yapi, Thozamile Steve. "An assessment of the impacts of invasive Australian wattle species on grazing provision and livestock production in South Africa." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/95455.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: I investigated the impacts of the invasive wattle species (Acacia mearnsii, A. dealbata, A. decurrens), on the ecological function and productivity of rangelands in South Africa and their ability to sustain livestock production. More specifically, this study set out to: (1) assess grazing areas at a national scale; (2) identify evidence of progressive impacts of these species on livestock production across a selection of magisterial districts; (3) determine the effects of A. mearnsii density on growth form dominance of indigenous plant species, and highlight how this translates into impacts in forage quality and quantity; (4) determine the effects of A. mearnsii invasion on soil resources and conditions (key determinates of ecological function) required to support grazing production; and finally (5) determine to effects that clearing operations have had on the provision of grazing resources. My results indicate that the level of overlap between wattle invasion and areas with a high grazing potential, at the national scale, is relatively low (2.9%). However, at a magisterial district scale, areas with a high grazing potential have a moderate (approximately 35.1% high grazing potential area under wattle invasion for highest invaded district) level of invasion. Scattered and moderate levels of invasion currently dominate or characterise these species invasion patterns. Both light and dense A. mearnsii invasions reduce grazing capacity. Dense invasion had the most severe effect reducing grazing capacity from 2 ha, required to support one large stock unit, to 8 ha. The clearing of this species was found to improve grazing capacity within 5 years. The reduction in grazing capacity following invasion was largely due to reduced basal cover and herbaceous biomass. The clearing of invaded sites was found to increase both basal cover and herbaceous biomass to pre-invasion levels. Acacia mearnsii invasion was found to affect certain soil properties. Under an A. mearnsii canopy, plant litter, carbon content of the soil and nitrogen concentrations were all found to be elevated. Overall, this study demonstrates that Acacia invasions have a significant effect on grazing resources at a local or site scale, and that for the eastern region of South Africa, these effects are ultimately scaled up to a district level. This is likely to have important financial and human well-being repercussions. However clearing and restoration programs are clearly able to reverse or mitigate these effects. This study therefore lends support to or complements other ecosystem service provision arguments for clearing alien invasive species.
AFRIKAANSE OPSOMMING: Die impak van die indringer- wattelbome spesies ( A. mearnsii , A. dealbata , A. decurrens) , op die ekologiese funksie en produktiwiteit van weivelde in Suid-Afrika en hul vermoë om vee produksie te onderhou was ondersoek. Meer spesifiek, is hierdie studie uiteengesit om: (1) ondersoek in te stel na die mate van oorvleueling tussen indringing deur wattelbome spesies en belangrike weidingsgebiede op 'n nasionale skaal; (2) bewyse te verskaf van die progressiewe impak van hierdie spesies op vee-produksie oor 'n seleksie van politieke distrikte, (3) die gevolge van A. mearnsii digtheid op groei vorm en oorheersing van inheemse plante te wys, en hoe dit voer kwaliteit en kwantiteit affekteer; (4) die gevolge van A. mearnsii indringing op grond hulpbronne sowel as die kondisie (sleutel bepalende faktore van ekologiese funksie) wat benodig word om weiding produksie te ondersteun vas te stel, en uiteindelik (5) om die gevolge van skoonmaak bedrywighede op die voorsiening van weiding hulpbronne te bepaaal. My resultate dui daarop dat die vlak van oorvleueling tussen die wattelbome indringing en gebiede met 'n hoë weiding potensiaal, by die nasionale skaal, relatief laag is (2’9 %). Maar op 'n landdrosdistrik skaal, het gebiede met 'n hoë weiding potensiaal 'n matige (ongeveer 35.1 % weiding potensiaal area onder wattelbome indringing vir die hoogste binnegevalde distrik ) vlak van indringing. Verspreide en matige vlakke van indringing oorheers tans of kenmerk hierdie spesies se indringings patrone. Beide lig en digte A. mearnsii besettings verminder dravermoë. Digte inval het die mees ernstige uitwerking en verminder dravermoë van 2 ha, wat nodig is om een grootvee-eenheid te ondersteun na 8 ha. Bevindinge wys dat die verwydering van hierdie spesies weiding kapasiteit kan verbeter binne 'n tydperk van 5 jaar. Die afname in dravermoë na indringing is grootliks te wyte aan die afname in basale bedekking en kruidagtige biomassa. Na die skoonmaak van indringer persele is bevind dat beide basale bedekking en biomassa weer verhoog tot voor- indringings vlakke. Acacia mearnsii indringing beïnvloed sekere grondeienskappe. Onder A. mearnsii blaredak, is alle blaarafval, koolstof-inhoud van die grond en stikstof konsentrasies verhef. In die algeheel, toon hierdie studie dat die Acacia indringings 'n beduidende uitwerking op weidings hulpbronne by 'n plaaslike of perseel skaal het, en vir die oostelike streek van Suid-Afrika, is hierdie effekte ook uiteindelik vertaalbaar tot 'n distrik vlak. Dit sal waarskynlik belangrike finansiële en menslike welsyn gevolge hê, maar die skoonmaak en herstel programme is duidelik daartoe instaat om die gevolge te keer of te verminder. Hierdie studie leen dus ondersteuning aan of komplimenteer ander ekostelsel dienslewering argumente (soos dié van die Werk vir Water program) vir die verwydering van indringerspesies.
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Robinson, Todd Peter. "Application of advanced techniques for the remote detection, modelling and spatial analysis of mesquite (prosopis spp.) invasion in Western Australia." Curtin University of Technology, Department of Spatial Sciences, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=118290.
Full textAbstract:
Invasive plants pose serious threats to economic, social and environmental interests throughout the world. Developing strategies for their management requires a range of information that is often impractical to collect from ground based surveys. In other cases, such as retrospective analyses of historical invasion rates and patterns, data is rarely, if ever, available from such surveys. Instead, historical archives of remotely sensed imagery provides one of the only existing records, and are used in this research to determine invasion rates and reconstruct invasion patterns of a ca 70 year old exotic mesquite population (Leguminoseae: Prosopis spp.) in the Pilbara Region of Western Australia, thereby helping to identify ways to reduce spread and infill. A model was then developed using this, and other, information to predict which parts of the Pilbara are most a risk. This information can assist in identifying areas requiring the most vigilant intervention and pre-emptive measures. Precise information of the location and areal extent of an invasive species is also crucial for land managers and policy makers for crafting management strategies aimed at control, confinement or eradication of some or all of the population. Therefore, the third component of this research was to develop and test high spectral and spatial resolution airborne imagery as a potential monitoring tool for tracking changes at various intervals and quantifying the effectiveness of management strategies adopted. To this end, high spatial resolution digital multispectral imagery (4 channels, 1 m spatial resolution) and hyperspectral imagery (126 channels, 3 m spatial resolution) was acquired and compared for its potential for distinguishing mesquite from coexisting species and land covers.These three modules of research are summarised hereafter. To examine the rates and patterns of mesquite invasion through space and time, canopies were extracted from a temporal series of panchromatic aerial photography over an area of 450 ha using unsupervised classification. Non-mesquite trees and shrubs were not discernible from mesquite using this imagery (or technique) and so were masked out using an image acquired prior to invasion. The accuracy of the mesquite extractions were corroborated in the field and found to be high (R2 = 0.98, P<0.001); however, accuracy varied between classes (R2 = 0.55 to 0.95). Additional sampling may be required in some of the wider class intervals, particularly the moderate density class (30 to 90%) as sampling frequency was poor within the range of 60 to 90%. This is a direct result of there being relatively few quadrats available to be randomly selected in this class. That is, quadrats with between 60-90% cover were only evident in 4% of the test area. A more robust approach would, therefore, be to split this class into two (e.g. 30-60% and 60-90%) and select an additional 15 quadrats in the 60-90% range. The resolution of the imagery (1.4 m) precluded mapping shrubs smaller than 3 m2. Rates and patterns were compared to mesquite invasions in its native range.
It was determined that: (i) the shift from grass to mesquite domination had been rapid, with rates of increase in canopy cover comparable to invasive populations where it is native; (ii) rate of patch recruitment was high in all land types (stony flats, red-loamy soils and the riparian zone), but patch expansion and coalescence primarily occurred over the riparian zone and redloamy soils; (iii) mesquite had been spread by sheep and macropods and the recent switch to cattle is likely to exacerbate spread as it is a far more effective dispersal vector; and (iv) early successional patterns, such as high patch initiation followed by coalescence of existing stands are similar to where mesquite is native, but patch mortality did not occur. A knowledge based model was used to predict which parts of the Pilbara region are most at risk. Several limitations of models often employed in predicting suitability ranges of invasive plants were identified and include: (i) an inability to incorporate the notion that within a suitability range there is likely to be a scale of favourability; (ii) an inability to assign greater importance to evidence that is likely to have more importance in defining the areas suitable for invasion; and (iii) an inability to control the level of conservatism in the final results. These three shortcomings were mitigated through the use of: (i) fuzzy membership functions to derive a range of favourability from poor to best; (ii) pairwise comparison to derive higher weights for layers perceived to be more important and vice versa; and (iii) the use of ordered weighted averaging to directly control the level of conservatism (or risk) inherent in the models produced.
Based on the outcomes of the historical reconstruction of spatial rates and patterns, data sources included land types, land use, and the derivation of a steady state wetness index from spot height data. Model outputs were evaluated using two methods: the area under the curves (AUC) produced from relative operating characteristic (ROC) plots and by the maximum Kappa procedure. Both techniques agreed that the model most representative of the validation data was the one assuming the most risk. To create a Boolean output representing areas suitable/not suitable for invasion, optimal cut-points were derived using the point closest to the top left hand corner of the ROC plot and by the maximum Kappa method. Both methods obtained identical cut-points, but it is argued that the coefficient produced by the maximum Kappa method is more easily interpreted. The highest AUC was found to be 0.87 and, based on the maximum Kappa method, can be described as good to very good agreement with the validation records used. Digital multispectral imagery (DMSI), acquired in the visible and near infrared portions of the spectrum (3 visible bands, 1 near infrared) with a spatial resolution of 1 m and hyperspectral imagery (126 bands, 3 m spatial resolution) was acquired to assess the potential of developing a reliable and repeatable mapping tool to facilitate the monitoring of spread and the effects of control efforts. Woody vegetation was extracted from the images using unsupervised classification and grouped into patches based on contiguity. Various statistics (e.g. maximum, minimum, median, mean, standard deviation, majority and variety) were assigned to these patches to garner more information for species separation.
These statistics were explored for their ability to separate mesquite from coexisting species using Tukey’s Honestly Significantly Different (HSD) test and, to reduce redundancy, followed by linear discriminant analysis. Two approaches were taken to select the patch statistics offering the best discrimination. The first approach selected patch statistics that best discriminated all species (named “overall separation”). This was compared to a second approach, which selected the best patch statistics that separated each species from mesquite on a pairwise basis (named “pairwise separation”). The statistics offering the best discrimination were used as input in an Artificial Neural Network (ANN) to assign class labels. An incremental cover evaluation, whereby producer’s accuracy was computed from mesquite patches grouped into various size-classes, showed that identification of mesquite patches smaller than 36 m2 was relatively low (43-51%) regardless of the method used for choosing between the patch statistics or image type. Accuracy improved for patches >36 m2 (66-94%) with both approaches and image types. However, both approaches used on the hyperspectral imagery were more reliable at capturing patches >36 m2 than the DMSI using either approach. The lowest omission and commission rates were obtained using pairwise separation on the hyperspectral imagery, which was significantly more accurate than DMSI using an overall separation approach (Z=2.78, P<0.05), but no significant differences were found between pairwise separation used on either media.
Consequently, all methods and imagery types, except for DMSI processed using overall separation, are capable of accurately mapping mesquite patches >36 m2. However, hyperspectral imagery processed using pairwise separation appears to be superior, even though not statistically different to hyperspectral imagery processed using overall separation or DMSI processed using pairwise separation at the 95% confidence level. Mapping smaller patches may require the use of very high spatial resolution imagery, such as that achievable from unmanned airborne vehicles, coupled with a hyperspectral instrument. Alternatively, management may continue to rely on visual airborne surveys flown at low altitude and speed, which have proven to be capable at mapping small and isolated mesquite shrubs in the study area used in this research.
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Meffin, Ross. "Invasion success and impacts of Hieracium lepidulum in a New Zealand tussock grassland and montane forest." Lincoln University, 2010. http://hdl.handle.net/10182/1808.
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Invasive species represent a major concern; they can result in serious ecological and economic losses and are recognised as one of the most serious threats to global species diversity. Plant invasions are of particular concern in New Zealand, which has high proportions of both naturalised and endemic plant species. In this thesis I focussed on the invasive plant Hieracium lepidulum, an exotic weed introduced from Europe to New Zealand prior to 1941. It is invasive in a variety of habitats in the South Island, where it has steadily increased in distribution and abundance over the last 50 years, and is thought to have detrimental impacts on native plant communities. I investigated factors influencing its invasion success and tested for impacts on native plant communities, making extensive use of existing plots into which H. lepidulum was experimentally introduced in 2003. I examined how community richness, turnover, resource availability and propagule pressure of the invader interacted to determine the invasion success of H. lepidulum. Results differed markedly above and below treeline. Above treeline, plots with higher richness and turnover were more invaded; below treeline, plots with higher available light were more invaded. In both habitats, these findings were modified by the influence of propagule pressure; at low propagule pressure, site characteristics were non-significant in explaining invasion success, while at higher propagule pressure these effects became significant. To test for impacts resulting in altered community composition and structure, I looked for changes in community richness, diversity and evenness subsequent to H. lepidulum introduction. As impacts may be more apparent at fine spatial scales, I made measurements at a 5 x 5 cm cell scale in addition to the established 30 x 30 cm plot scale. Plot species richness increased from 2003 to 2009 and a component of this increase was associated with H. lepidulum density. Other relationships between the plant community and H. lepidulum were generally non-significant. Results showed that H. lepidulum has had no negative effects on community richness, evenness or diversity. Despite being able to opportunistically colonise grassland sites with high turnover, and forest sites subject to canopy disturbance, dependant on propagule pressure, it appears H. lepidulum has not impacted community composition or structure.
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Saulnier, Ronald Betnoit. "Analysis of integrins and cell adhesion on invasive tumor cell lines using an in vitro invasion assay." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30317.
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Little is known about the mechanisms which cause tumor cells to become invasive. For this thesis an in vitro tumor cell invasion assay was developed and used to investigate the role of a family of cell surface receptors, called integrins, in the invasion of tumor cells across basement membranes. It was also used to isolate an invasive cell line in order to study some of its properties.
Two osteosarcoma cell lines, HOS and MNNG-HOS, with known in vivo metastatic potentials were assayed in the in vitro invasion assay. Invariably, the highly tumorigenic and metastatic MNNG-HOS cells demonstrated greater invasive ability than the non-tumorigenic HOS cells. The chemical transformation of HOS into tumorigenic MNNG-HOS cells resulted in an increase in the expression of α₁β₁, α₂β₁ and α₆β₁ integrins which are laminin and collagen receptors. The expression of α₃β₁ and α₅β₁, were unchanged on MNNG-HOS cells and the expression of αvβ₃ was strongly downregulated on the more invasive cells. The invasion of HOS and MNNG-HOS cells through matrigel could be significantly inhibited when anti-fibronectin receptor or anti-α₆ subunit antibodies were present in the invasion assay, demonstrating the important role of integrins in tumor cell invasion.
The in vitro invasion assay described in this thesis was used to isolate a more invasive cell line from the prostate carcinoma cell line, PC-3, and called IPC-3. The morphology of these cells was distinct from the parent population, showing a spherical morphology as opposed to the triangular or spindle shaped morphology of PC-3 cells. These cells were also several times more invasive than the PC-3 cells and proliferated at a faster rate than the parent PC-3 cells. IPC-3 cells gradually lost their invasive potential after several months in tissue culture but retained their morphology and the characteristic expression of integrins. Adhesion of PC-3 and IPC-3 cells to purified extracellular matrix components revealed that IPC-3 attached well to laminin and to vitronectin. In adhesion kinetic experiments to purified extracellular matrix proteins, IPC-3 cells attached more quickly than PC-3 cells to larninin and vitronectin. Although the IPC-3 cells attached to the extracellular matrix proteins, fibronectin, vitronectin, laminin and collagen type IV, they were only able to spread on laminin and required several hours to do so. PC-3 cells also attached well to the extracellular matrix proteins but required only several minutes to spread on the matrix proteins including laminin. When plated on stock matrigel PC-3 cells organized themselves in tube-like structures while IPC-3 cells aggregated in clusters.
Analysis of the integrins on PC-3 and IPC-3 cells demonstrated that IPC-3 cells downregulated the expression of the α₁β₁,α₂β₁ and an almost completely downregulated the α₃β₁ integrin while the expression of the fibronectin receptor, α₅β₁,, and the vitronectin receptor, αⅴβ₁, were unchanged. The expression of α₆β₁, in both PC-3 and IPC-3 cells was not prominent. However the α₆β₄ receptor was present in large amounts and was upregulated in IPC-3 cells, particularly the 200 kDa subunit of β₄.
Immunofluorescence staining of PC-3 and IPC-3 cells demonstrated that PC-3 cells distributed their α₃β₁ and α₆β₄ integrin receptors mainly along the cell periphery and their αⅴβ₃ receptor in focal adhesion plaques, while the invasive IPC-3 cells concentrated their integrin receptors in circular adhesion structures.
Although much remains to be learned about integrins, they have an instrumental role in the invasion of tumor cells across basement membranes during the metastatic cascade of malignant cells.Medicine, Faculty of
Pathology and Laboratory Medicine, Department of
Graduate
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Kempf, Hannah Lowe. "Comparisons of Ecosystem Dynamics Before and After Invasion Reveal Consequences of Invasive Species in Benthic Marine Communities." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1524830000208304.
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Ramakrishnan, Alisa Paulsen. "Genetic patterns of dispersal and colonization during initial invasion and spread of an invasive grass, Brachypodium sylvaticum." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/355.
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Evolution of genotypes during range expansion is driven in part by colonization dynamics. I investigated genetic patterns of colonization and dispersal during initial expansion of an invasive bunchgrass, Brachypodium sylvaticum, into Oregon. Using microsatellite markers, I sampled plants at two different scales: at regular intervals along three parallel roads spanning about 30km, and in populations identified throughout Oregon. I also collected field-generated progeny from a subset of populations and used molecular identification of outcrossing events to estimate selfing rates in both central and peripheral populations. Dispersal patterns were similar at both scales, with non-contiguous dispersal responsible for colonization of new populations. High levels of differentiation were observed at all scales, though newly-colonized populations were more differentiated than older populations. Corvallis populations were responsible for colonization of a majority of populations throughout Oregon, while individuals from Eugene were only occasionally found in new populations. Admixture occurs between Corvallis and Eugene populations, decreasing differentiation, and potentially creating novel phenotypes and increasing evolutionary potential of populations. Selfing rates were high, but two populations in the areas of original introduction had lower rates of selfing, suggesting that selfing rates may decrease as population density and diversity increases with age. The influences of founder effects and bottlenecks on phenotypic evolution during range expansion require further investigation, as inbreeding, lag times, and selection may influence evolutionary trajectories of populations.
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Murphy, Jennifer E. "The Beginning and Legacy of Rosa multiflora Invasions: Understanding the Mechanisms that Drive Its Success Across Stages of Invasion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1561484787925341.
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Kelley, Amanda. "The Effect of Temperature on Phenotypes of the Invasive European Green Crab: Physiologic Mechanisms that Facilitate Invasion Success." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1004.
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Invasion physiology is an emerging field that endeavors to understand the influence of physiological traits on the establishment of non-native species in novel environments. The invasive European green crab,Carcinus maenas, is one of the world's most successful aquatic invaders, and is currently distributed across temperate marine ecosystems globally. The work presented here explored the thermal physiology of this species, and has highlighted several physiological traits that have likely influenced establishment success.
Intraspecific comparisons of crabs sampled from the northern and southern edges of their recipient, or invaded range on the west coast of North America have identified both organismal and cellular physiological difference with respect to upper and lower thermal tolerances. Crabs sampled from British Columbia, Canada (BC) had a significantly lower mean upper thermal tolerance threshold and heat shock protein synthesis, Hsp70, compared to their warm acclimated conspecifics sampled from California (CA). These differential physiologic responses may be rooted in the disparate natural thermal habitats that each population occupies within their respective environments.
The ability of this species to extend its current range limits was also investigated. Range expansion to the south has been limited, and is likely restricted by this species lack of adaptation to warmer temperatures. Because range expansion has been chiefly northward, characterizing this species' response to cold stress can identify whether colder temperatures poleward may limit further range expansion. Cold tolerance capacity was determined in the laboratory, and crabs sampled from Vancouver Island, British Columbia were able to withstand the over-wintering thermal regime that occurs in Sitka, Alaska, a site that is currently beyond the range limits of this species. Furthermore, intraspecific assessments found that the cold acclimated BC population exposed to cold shock significantly down regulated protein levels of cyclin D1, cell cycle modulator.
Distinct differences in carapace width (CW) were detected along the thermal gradient present in the green crabs' range. This variation in body size was utilized to the test the temperature size rule hypothesis for ectotherms. Simply stated, the temperature size rule is the tendency for ectotherms to develop slower but mature to a larger body sizes at cooler temperatures. The results supported this hypothesis as crabs sampled from the warm portion of the range were found to be smaller than crabs sampled from the colder portion of the range. This pattern was detected along the native range as well. Differences in body size have the potential to influence the scope of invasion; larger individuals are generally more fecund and longer lived, which can increase both the intensity and frequency of larval dispersal that could further propel range expansion.
The physiologic properties that the green crab possesses which may influence invasion success were examined using peer-reviewed literature with the aim of determining if these physiological traits confer invasion success across taxa. This analysis tested four hypotheses: 1) Broad geographic temperature tolerances (thermal width) confer a higher upper thermal tolerance threshold when comparing invasive and native species. 2) The upper thermal extreme experienced in nature is correlated with upper thermal tolerance threshold. 3) Protein chaperone expression, a cellular mechanism underlying thermal tolerance threshold, is greater in invasive organisms than in native ones. 4) Acclimation to higher temperatures can promote a greater range of thermal tolerance for invasives compared to natives. These preliminary results generally support the four stated hypotheses, and provide a solid foundation for further studies to explore and identify physiologic traits that facilitate invasion success.
Overall, these studies investigated the thermal physiology ofCarcinus maenasfrom an invasive metapopulation and have brought about significant advances in our understanding of what physiologic traits correlate to invasion success in this species. In addition, the data presented here can aid resource managers in identifying habitats, based on thermal tolerance measurements that fit the criteria for invasion. Understanding how invasive organisms vary with respect to thermal tolerance can aid our understanding the patterns and processes of species invasions.
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Mastalerz, Allison. "The role of ornamental gardening in forest plant invasions across an urban-rural gradient in Southwestern Ohio." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377866412.
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Vardien, Waafeka. "Molecular ecology and invasive species management: unravelling the dynamics of Lantana camara invasions in the Kruger National Park, South Africa using a molecular approach." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20378.
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Thesis (MSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Non-native species are recognized as a major component of global environmental change. Their ecological impacts are numerous and include the alteration of whole ecosystem processes as well as the loss of native biodiversity. As such, understanding the processes that drive the invasion of non-native species is essential for the control and management thereof. Numerous research approaches have been used to provide insight on the history and ecology of non-native species invasions. However, recent approaches employing molecular techniques have greatly helped in solving taxonomic issues associated with some of these species; identifying sources of invasions; and shedding light on colonization dynamics. Lantana camara, a globally invasive and highly variable species complex, is one of the most notorious plant invaders in South Africa. The species has been associated with negative impacts in agricultural areas, decreased invertebrate diversity, livestock mortality, and where it occurs along riparian areas- decreased water quality and obstruction to accessing water sources. This project aimed to review L. camara invasions in South Africa and to unravel patterns of spread in L. camara along the Sabie-Sand catchment in South Africa’s flagship protected area, the Kruger National Park, using a molecular approach. The findings of the first part of the study highlight that L. camara has successfully spread across South Africa with only four known introduction events, and this can be attributed to the species’ broad ecological tolerance, its use in the horticultural industry, and a variety of dispersal vectors (birds, humans and rivers). Furthermore, although sale of the species is prohibited in the country, it will continue to spread naturally and also has the potential to expand its distribution under changing climate scenarios. The second part of the study highlights that spread along the Sabie-Sand catchment is primarily river-driven and that the Sand tributary is the invasion source in the system. Because the Sand tributary originates outside the Kruger National Park, and only a small portion is under park management, the implications for spread are important.
AFRIKAANSE OPSOMMING: Nie-inheemse spesies word erken as 'n belangrike komponent van die globale omgewing verandering. Hulle ekologiese impak is talle en sluit in die verandering van ekosisteem prosesse asook die verlies van inheemse biodiversiteit. As sodanig, die begrip van die prosesse wat lei tot die inval van 'n nie-inheemse spesies is noodsaaklik vir die beheer en bestuur daarvan. Talle navorsingsbenaderings is gebruik om insig te gee oor die geskiedenis en ekologie van nie-inheemse spesies invalle. Onlangse benaderings soos die gebruik van molekulêre tegnieke, help in die oplossing van taksonomiese kwessies wat verband hou met 'n paar van hierdie spesies,in die identifisering van bronne van invalle, en om lig te werp op die kolonisasie dinamika. Lantana camara, 'n wêreldwye indringende en spesie kompleks, is een van die mees berugte plantindringer in Suid-Afrika. Die spesie is geassosieer met negatiewe gevolge in landbou gebiede, afgeneem ongewerwelde diversiteit, vee mortaliteit, en waar dit voorkom saam oewer gebiede - afgeneem kwaliteit van die water en obstruksie tot waterbronne. Hierdie projek is daarop gemik om om L. camara invalle in Suid-Afrika te hersien en patrone van verspreiding te ontrafel in L. camara langs die Sabie-Sand-opvanggebied in Suid-Afrika se vlagskip beskermde gebied, die Kruger Nasionale Park, met behulp van 'n molekulêre benadering. Die bevindinge van die eerste deel van die studie wys dat L. camara het suksesvol versprei oor die hele Suid-Afrika met slegs vier bekende inleiding gebeure, en dit kan toegeskryf word aan die spesie se breë ekologiese verdraagsaamheid, die gebruik daarvan in die hortologie bedryf, en 'n verskeidenheid van die verspreiding vektore (voëls, mens en riviere). Verder, hoewel die verkoop van die spesie in die land verbied word, sal dit natuurlik voortgaan om te versprei en het ook die potensiaal om uit te brui onder veranderende klimaat scenario's. Die tweede deel van die studie wys dat versprei langs die Sabie-Sandopvanggebied hoofsaaklik rivier-gedrewe is en dat die Sand sytak die inval bron is. Omdat die Sand sytak buite die Kruger Nasionale Park ontstaan, en slegs 'n klein gedeelte onder park bestuur is, is die implikasies vir verspreiding belangrik.
Financial support from the DST-NRF Centre of Excellence for Invasion Biology and the Working for Water (WfW) Programme through their collaborative project on “Research for Integrated Management of Invasive Alien Species” and Stellenbosch University’s Subcommittee B Young Researcher's Fund
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Parker, John D. "Plant-herbivore interactions : consequences for the structure of freshwater communities and exotic plant invasions." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/9460.
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Invasive exotic species threaten native biodiversity, alter ecosystem structure and function, and annually cost over $100 billion in the US alone. Determining the ecological traits and interactions that affect invasion success are thus critical for predicting, preventing, and mitigating the negative effects of biological invasions. Native herbivores are widely assumed to facilitate exotic plant invasions by preferentially consuming native plants and avoiding exotic plants. Here, I use freshwater plant communities scattered broadly across the Southeastern U.S. to show that herbivory is an important force driving the ecology and evolution of freshwater systems. However, native consumers often preferentially consume rather than avoid exotic over native plants. Analyses of 3 terrestrial datasets showed similar patterns, with native herbivores generally preferring exotic plants. Thus, exotic plants appear defensively nave against these evolutionarily novel consumers, and exotic plants may escape their coevolved, specialist herbivores only to be preferentially consumed by the native generalist herbivores in their new ranges. In further support of this hypothesis, a meta-analysis of 71 manipulative field studies including over 100 exotic plant species and 400 native plant species from terrestrial, aquatic, and marine systems revealed that native herbivores strongly suppressed exotic plants, while exotic herbivores enhanced the abundance and species richness of exotic plants by suppressing native plants. Both outcomes are consistent with the hypothesis that prey are susceptible to evolutionarily novel consumers. Thus, native herbivores provide biotic resistance to plant invasions, but the widespread replacement of native with exotic herbivores eliminates this ecosystem service, facilitates plant invasions, and triggers an invasional meltdown. Consequently, rather than thriving because they escape their co-evolved specialist herbivores, exotic plants may thrive because their co-evolved generalist herbivores have stronger negative effects on evolutionarily nave, native plants.
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Olsson, David. "USA:s invasion av Irak : EN studie av hur Bushadministrationen motiverade invasionen av Irak 2003, och hur motiveringen förhåller sig till FN-stadgan." Thesis, Försvarshögskolan, Krigsvetenskapliga avdelningen (KVA), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-2701.
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2003 invaderade USA tillsammans med ett antal av dess allierade Irak. Invasionen genomfördes utan mandat från FN:s säkerhetsråd. Uppsatsen handlar om hur USA och Bushadministrationen motiverade den invasionen och om hur FN:s och FN-stadgans regelverk reglerar internationell våldsanvändning.Syfte med uppsatsen är att se hur Bushadministrationens motiveringar förhåller sig till FN-stadgan och till den tillhörande resolutioner.Detta har gjorts genom en kvalitativ textanalys där tal och officiella dokument analyserats. Som teoretisk grund har realismen använts. Realismen har även använts som en förklaringsmodell för varför USA handlade som de gjorde.Resultatet i uppsatsen visar att USA:s invasion av Irak 2003 ej var förenlig med FN-stadgan och till den tillhörande resolutioner. Men tydliga kopplingar mellan USA:s aggerande och Realismen kan identifieras.
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Brown, Carly. "Applications of DNA-barcoding in the identification and understanding of grass invasions in Southern Africa." Thesis, University of the Western Cape, 2014. http://hdl.handle.net/11394/4650.
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Magister Scientiae (Biodiversity and Conservation Biology)The spread of invasive species is one of the greatest threats to global biodiversity. Alien plant invasions also have serious economic impact in terms of the delivery of ecosystem goods and services. Studies of biological invasions in southern Africa have tended to overlook grasses (family Poaceae), although there are many naturalised species in the region. Only a few of these, all perennials, have been officially categorised as invasive in South Africa, but in the winter rainfall region of the Western Cape, grass invasion especially by Mediterranean European annuals have also been noted. These grasses can be difficult to identify. DNA barcoding has been suggested as an alternative method of identifying grasses in the hope of facilitating identification of existing invaders and preventing future invasions. In this study a list of all known naturalised grasses in South Africa was compiled, and a DNA barcoding reference database was assembled for these naturalised grass species as well as for native southern African grass species. The two official markers for plant DNA barcoding (rbcLa + matK) were used in barcoding and phylogenetic analyses, both individually and in combination. The barcoding data was assessed for identification efficacy using three distance-based metrics and one tree-based metric in the R package SPIDER, both including and excluding singleton data. This study lists 128 naturalised grass species and subspecies found in South Africa. In the DNA barcoding analyses, matK was found to perform better as a single barcode than rbcLa, with identification success rates of up to 84% for matK and 76% for rbcLa, using the most successful metric which was the Nearest Neighbour criterion for both of these markers in the data sets without singletons. The combined rbcLa + matK data set performed better than either of the two individual markers, with identification success rates of up to 91% in the data without singletons, with the most successful metric again being the Nearest Neighbour criterion. The combined rbcLa + matK data would therefore be the recommended DNA barcode for southern African grasses of the three data sets tested, based on the results of this study. Phylogenetic trees were constructed with the DNA barcoding data using Bayesian Inference (BI) and Maximum Parsimony (MP) to assess the usefulness of the data in phylogenetic studies and to confirm the efficacy of this grass DNA barcoding data when using tree-based methods of identification. Both the matK and combined datasets resolved all of the grass tribes represented in this study as monophyletic, but the rbcLa data did not.
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Soria, Carvajal Monica Cecilia. "Avian seed dispersers of the invasive Rubus niveus (Rosaceae) in Santa Cruz Island, Galapagos, Ecuador." Diss., St. Louis, Mo. : University of Missouri--St. Louis, 2006. http://etd.umsl.edu/r1761.
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Richards, Jeannine Hyde. "From 'useful and interesting' to 'evil invaders': evolving perceptions of non-native species in the United States." Thesis, Boston University, 2002. https://hdl.handle.net/2144/27749.
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Boston University. University Professors Program Senior theses.PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
2031-01-02
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Alba, Castellón Lorena 1984. "Snail1 expression in mesenchimal cells promotes tumorigenesis and tumor progression." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/403887.
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Snail transcription factor 1 triggers epithelial to mesenchymal transition. In cancer, this process provides tumoral epithelial cells with invasive characteristics. In this thesis, we demonstrated that the function of Snail1 in fibroblasts and mesenchymal stem cells (MSCs) also contributes to tumor progression. In tumors with a mesenchymal origin, expression of Snail1 in oncogenic MSCs is needed to maintain their tumorigenic capacity and is required in vivo for tumor formation. Therefore, its deletion results in the absence of tumors. In tumors with an epithelial origin, we demonstrated that Snail1 expression in stromal fibroblasts is required to promote tumor cell invasion. Fibroblasts are activated in a Snail1-dependent manner by factors such as TGF- released by epithelial tumor cells. As response, fibroblasts secrete prostaglandin E2 which contributes to tumor invasion. Consequently, depletion of Snail1 in in vivo cancer models reduces the invasion to adjacent tissues and decreases metastasis. These results suggest a key role for Snail1 in tumor progression that is not limited to its expression in epithelial cells.El factor de transcripción Snail1 es necesario para iniciar la transición epitelio-mesénquima. En cáncer, este proceso provee a las células epiteliales tumorales con características invasivas. En esta tesis demostramos que la función de Snail1 en fibroblastos y en células madre mesenquimales (MSCs) también contribuye a la progresión tumoral. En tumores de origen mesenquimal la expresión de Snail1 en MSCs es necesaria para mantener sus capacidades tumorigénicas e in vivo es necesaria para la formación del tumor. En tumores de origen epitelial, la expresión de Snail1 en los fibroblastos del estroma es necesaria para promover la invasión de las células tumorales. Los fibroblastos son activados de manera dependiente de Snail1 gracias a factores liberados por las células epiteliales del tumor; por ejemplo TGF-. Uno de los efectos de esta activación es la secreción de prostaglandina E2 la cual contribuye a la invasión tumoral. En consecuencia, la depleción de Snail1 en modelos tumorales in vivo reduce la invasión a tejidos adyacentes y disminuye la aparición de metástasis. Estos resultados sugieren un rol clave de Snail1 durante la progresión tumoral que no está limitado a su expresión en células epiteliales.
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Devine, Kevin Patrick. "INITIAL RESPONSE OF INVASIVE EXOTIC PLANT SPECIES TO TIMBER HARVESTING IN SOUTHEASTERN KENTUCKY FORESTS." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/650.
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The responses of invasive exotic plant species (IES) to silvicultural treatments one growing season after timber harvesting were examined in the Cumberland Plateau region of Southeastern Kentucky. Treatments included a commercial deferment harvest and unharvested control applied to five watersheds within University of Kentucky’s Robinson Forest. The effects of harvesting were compared between treatments and between preharvest and postharvest samplings. The spatial distribution and abundance of targeted IES throughout forest sites and trail systems were calculated from several sampling schemes. Additional analyses were performed to quantify forest disturbances derived from harvest activities to determine the relationships between soil, light levels, and other environmental characteristics and IES cover. Logistic and multivariate analysis techniques were used to analyze differences in IES distribution between pre-harvest and post-harvest units to relate post-harvest IES to microsite conditions. Microsite conditions within the forest and along the trail system proved important for explaining the presence and distribution of IES. Timber harvesting caused a significant increase in both Ailanthus altissima and Microstegium vimineum within harvested areas. However, many other identified IES did not initially respond to disturbances. Throughout the treatment units, species were influenced by disturbance type and intensity, as well as proximity to reclaimed surface mined land.
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Bohl, Kerry. "An investigation of the factors leading to invasion success of non-native plants using a system of native, introduced non-invasive, and invasive Eugenia congeners in Florida." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4442.
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The overwhelming majority of plant species introduced into a new range never become invasive. Consequently, identification of factors allowing the small fraction of successful invaders to naturalize, increase in abundance, and displace resident species continues to be a key area of research in invasion biology. Of the considerable number of hypotheses that have been proposed to resolve why some plant species become noxious pests, the enemy release hypothesis (ERH) is one of the most commonly cited. The ERH maintains that invasive plants succeed in a new range because they are no longer regulated by their coevolved natural enemies, and this reduction in enemy pressure imparts a competitive advantage over native species, which continue to be negatively impacted by top-down processes. Alternatively, the ability of invasive plant species to outperform their counterparts, rather than escape from enemies, may be key in conferring invasion success. The importance of preadapted traits and release from natural enemies in successful invasion remains unclear, likely owing to a lack of empirical studies comparing their effects on relative performance and population growth of closely related species that differ in origin and invasiveness. A system of co-occurring native, introduced non-invasive, and invasive Eugenia congeners exists in south Florida, providing an opportunity to address deficiencies in our understanding of plant invasions by investigating the factors leading to invasion success for Eugenia uniflora. This approach is novel because very few studies have simultaneously incorporated both native and introduced non-invasive congeners into tests of these hypotheses, and no others have done so using this system of Eugenia congeners.
The first study in this dissertation tested the ERH using an insect herbivore exclusion experiment in the field to compare the effects of natural enemies on the performance and population growth of Eugenia uniflora and its native congeners. The results showed that E. uniflora sustained more herbivore damage than its native counterparts, and that the effects of herbivores were sufficient to have negative impacts on performance and population growth. In sum, these findings contradict the ERH. Surprisingly, the vast majority of damage to E. uniflora was caused by the recently introduced Sri Lankan weevil (Myllocerus undatus), with which it shares no coevolutionary history. The second study compared seedling performance among native, introduced non-invasive, and invasive Eugenia congeners to determine if the success of E. uniflora can be attributed to superior performance traits. Invasive E. uniflora was found to outperform its native and introduced non-invasive counterparts in a number of seedling traits, including emergence, growth, and survival, in spite of sustaining higher levels of herbivore damage in the field. This result was consistent across years and sites, suggesting that superior performance may be an important factor in invasion success by E. uniflora. The final experiment investigated the role of enemy release on performance of native, introduced non-invasive, and introduced invasive Eugenia seedlings using an insect herbivore exclusion experiment in the field. In this study, the invasive E. uniflora was again found to sustain more damage by foliar herbivores compared to its native and introduced non-invasive counterparts. However, in spite of higher levels of herbivore damage, E. uniflora continued to outperform its congeners in terms of stem growth, and its congeners did not outperform E. uniflora in any attribute. Insect herbivores negatively affected survival of all species, but were found to have little effect on growth. In combination, the results of these studies indicate that the ability of E. uniflora to outperform its native and introduced congeners at the seedling stage, and not release from insect herbivores, may contribute to its success as an invader. Additionally, E. uniflora exhibits relatively low resistance to herbivory in the new range, and instead may possess an ability to tolerate moderate levels of damage. The implications of this study are that enemy release may not be important in determining invasion success in some systems, and that the accumulation of new enemies may mitigate the effects of invasive plants over time. The paucity of studies investigating interactions among invasive plants and herbivores that share no coevolutionary history warrants further research. Finally, this system of Eugenia congeners provides valuable opportunities to test additional hypotheses and to further explore factors leading to invasion success.
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Fletcher, David. "Biological invasion risk assessment, considering adaptation at multiple scales : the case of topmouth gudgeon Pseudorasbora parva." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG029/document.
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Afin de quantifier les risques d’invasion chez le goujon Asiatique Pseudorasbora parva, un petit cyprinidae d’eau douce, j’ai tout d’abord testé une approche corrélative de modélisation de la niche climatique dans laquelle j’ai intégré un proxy relatif à la probabilité d’introduction. Cette approche s’appuie sur des assomptions relatives à l’adaptation des organismes aux conditions environnementales locales ou régionales. J’ai ensuite comparé la niche climatique mesurée de deux lignées génétiques majeures à la fois dans les aires natives et envahies. Puis dans un second temps, par une approche expérimentale j’ai comparé la réponse aux variations de température, des traits d’histoire de vie de populations vivant dans des zones climatiques contrastées. Finalement, je me suis intéressé à la dispersion des goujons Asiatiques afin de mieux comprendre si les populations situées sur les fronts d’invasions avaient des capacités de colonisation plus importante. J’ai donc quantifié et comparé le long d’un gradient d’invasion, le potentiel de dispersion des individus ainsi que des traits pouvant y être liés (activité et morphologie). L’étude des risques d’invasions a montré que de nombreuses zones – au delà des zones déjà envahies - étaient climatiquement favorables au goujon Asiatique. C’était le cas en particulier pour certaines zones comme l’Australie, l’Amérique du Sud et du Nord, indiquant que l’invasion de cette espèce pourrait encore s’étendre. Après avoir pris en compte les probabilités d’introduction, cette étude a montré que l’Amérique du Nord était la zone la plus à risques. Par contre, la niche climatique entre les différentes lignées dans les zones géographiques envahies est très similaire, ce qui laisse à penser qu’il n’y a pas de patrons d’adaptation locale chez cette espèce. Pour autant, la niche climatique observée dans la zone envahie est très différente de celle observée dans la zone native, ce qui suggère un shift climatique important au cours de l’invasion. Les réponses thermiques des traits d’histoire de vie du goujon Asiatique testés expérimentalement n’ont pas varié significativement entre les populations originaires de conditions climatiques continentales et maritime-tempérées. Par exemple, l’effort reproductif global des femelles n’a pas varié entre les températures testées (15-25°C) mais la stratégie temporelle de reproduction a beaucoup varié. L’effort reproductif était plus cours et plus intense à forte température, alors qu’il était plus étalé et avec des pics reproductifs moins forts à faible température. Pour ailleurs, il semble qu’il existe un gradient morphologique fort entre les populations situées à différentes distances du front d’invasion ce qui suggère une forte plasticité morphologique mais qui ne serait pas liée à la capacité de dispersion de ces populations. En effet, cette dernière ne variant pas significativement le long du gradient d’invasion. La capacité de dispersion serait principalement liée à la taille du corps de goujon Asiatique, les individus les plus grands ayant une probabilité plus élevée de disperser.Bien que les prédictions générales du modèle de niche puissent être affectées par de potentielles adaptations à l’échelle de la population ou de la lignée évolutive, les résultats suggèrent qu’une certaine incertitude liée à ces prédictions persiste puisque la distribution native ne prédisait que très mal la distribution actuelle dans les zones envahies. Par ailleurs, mes travaux expérimentaux à plus fine échelle suggèrent que cette espèce est extrêmement adaptable et tolère une large gamme environnementale, ce qui pourrait expliquer son caractère invasif. Les connaissances produites au cours de cette thèse constituent donc des ressources extrêmement pertinentes pour développer des stratégies de gestion visant à contrôler les invasions futures du goujon AsiatiqueIn this thesis I set out to quantify the risk of invasion from the invasive freshwater fish, Pseudorasbora parva, at a global extent, using traditional correlative ecological niche modelling approaches with the integration of surrogate data representing introduction likelihood (Chapter I). These correlative approaches rely upon key assumptions relating to the presence or absence of local or regional adaptations, and so I subsequently tested for evidence of such adaptations in genetic lineages and in individual populations. This was achieved through analyzing climatic niche differentiation of key genetic lineages in the native and invasive ranges (Chapter II) and by conducting lab experiments comparing thermal responses of important life history traits in populations from contrasting climates (Chapter III). The initial risk assessment did not account for a key factor in invasions; namely, natural dispersal. Natural dispersal has been observed to be subject to selection in vanguard populations of invasive species, and adaptation of dispersal traits can infer additional invasive vigor, allowing the species to spread across the landscape quicker. For this reason, I quantified dispersal, activity and morphological differences, often associated with differential dispersal ability, in populations along a distance-gradient from an invasion front, in order to identify if P. parva is capable of such adaptations.The initial risk mapping study showed that large areas, beyond the current distribution of the species, are climatically suitable. These areas are mainly in North and South America, Australia and New Zealand, and constitute significant scope for spread and impact of this species. When introduction likelihood was included, N. America appears most at risk. I found no evidence to suggest that native genetic lineages represented local adaptations to their respective native climates - there was little or no differentiation of the lineages’ climatic niches in the invasive range. It was also apparent, from the niche comparisons, that the climatic niche in the invaded range constituted a significant shift, compared to the native range. The thermal responses of P. parva life history traits did not differ significantly between populations from a strongly seasonal continental climate and a mild temperate maritime climate. The overall reproductive output of females did not vary according to breeding season temperature, however, temporal reproductive strategy showed a strong response, with lower temperatures inducing a protracted breeding season and higher temperatures inducing rapid and intense reproductive output. The dispersal and morphology-related study identified a strong gradient of morphological change, corresponding with distance from invasion front. This demonstrates a high degree of plasticity in P. parva’s morphology in an invasion context, however this was not linked to either dispersal or activity levels, neither of which was significantly linked to distance from invasion front. Dispersal was best explained by body size, with larger fish more likely to disperse further.Whilst I found no evidence to suggest that the model predictions (Chapter I) were hampered by differentiation at either lineage or population levels, the findings of Chapter II do highlight the uncertainties surrounding the degree of conservatism in such predictions, mainly owing to the fact that past, native, distribution did not accurately predict the current invaded distribution. The results of Chapters II-IV show broad tolerances and great plasticity in P. parva, which likely underpin this species success as a pan-continental invader. The knowledge produced in this thesis provides a useful new resource for the development of management strategies for P. parva and could be usefully enhanced by the additional of analogous studies on native populations, which could help elucidate the source of the observed plasticity
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Thompson, Glen Andrew. "Mechanisms of invasion and persistence of the invasive kelp Undaria pinnatifida (Harvey) Suringar within intertidal areas of southern New Zealand." Thesis, University of Canterbury. Zoology, 2004. http://hdl.handle.net/10092/6875.
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Very few studies have examined the mechanisms of local establishment and persistence of invasive marine species, especially invasive seaweeds. Undaria pinnatifida, an invasive kelp from Japan, Korea and China was first discovered in New Zealand in 1987. Although U. pinnatifida's spread has been rapid, particularly along the east coast of southern New Zealand very little is known about how this species establishes and persists within invaded areas. This study is unique in that it determines some of the characteristics and mechanisms that enable Undaria pinnatifida to invade and persist in intertidal areas of southern New Zealand.
Demographic characteristics of U. pinnatifida were examined within the intertidal zone at four sites along the east coast of the South Island, New Zealand. Continual recruitment over this period resulted in the presence of mature plants and recruit plants during most of the year. However, although plants could be found year round at most sites, distinct cohorts were observed between autumn and spring at all sites. Plants were absent during most months of the summer at Rapaki Bay. Maximal growth occurred during the spring but periods of peak growth were variable, both temporally and spatially. Reproducing plants were found from mid winter to mid summer at most sites with peak reproduction occurring between the late spring and mid summer. Potential lifetime reproductive output of individual plants was approximately 10⁸-10⁹ spores and was related to sporophyll size. Plants with the largest sporophylls were found within the low zone at Moeraki Platform. The appearance of spring recruits suggests that autumn recruits may be able to reproduce by winter and provide a second generation during the same year.
Substratum removal experiments examining the ability of U. pinnatifida to recruit onto bare space and coralline turfs showed that coralline turfs facilitated recruitment. Large numbers of recruits were found within the coralline turfs regardless of timing of clearance or the size of clearance. Experiments on the survival of early postsettlement stages showed that facilitation may occur by the coralline turfs protecting embryonic sporophytes from harsh physical conditions such as desiccation whereas grazers had no effect on the survival of embryonic sporophytes.
Canopy removal experiments within stands of Carpophyllum maschalocarpum revealed that a combination of size and substrata were important in the recruitment of U. pinnatifida. After 12 months, small (5 x 5 cm) clearances had recovered to preinitiation canopy coverage. In contrast, the medium (25 x 25 cm) and larger (50 x 50 cm) clearances had a mixture of both C. maschalocarpum and U. pinnatifida. The differences observed between the size treatments were attributed to contrasting life histories and demographic characteristics.
Experimental removal of intra-specific and inter-specific canopies showed that U. pinnatifida is capable of recruiting very quickly after a canopy disturbance. This suggests that some form of "seed bank" may be present. Further experiments showed that it was likely the embryonic sporophytes were providing the means for rapid recruitment. Newly-developed embryonic sporophytes placed out in the field were visible after 3 months. This suggests a development period of approximately four months from spore release to visible recruit.
The results from this study suggest that demographic characteristics including rapid growth, high reproductive output and extended recruitment periods are important factors in the establishment and persistence of U. pinnatifida. However, life history characteristics including the ability of embryonic sporophytes to delay recruitment and the ability to produce two generations in one year are also considered important. The dominance of U. pinnatifida within the intertidal at the study sites is largely due to the ability to coexist with coralline turfs. Coralline turfs appear to facilitate recruitment of U. pinnatifida and coupled with its life history and demographic characteristics are probably the reason why U. pinnatifida can establish and persist within the intertidal along the east coast of the South Island, New Zealand.
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Essemyr, Moa, and Frida Persson. "INVASION DIREKTMARKNADSFÖRING." Thesis, Halmstad University, School of Business and Engineering (SET), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-732.
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Direct marketing is an area within marketing that is growing rapidly. Many companies has realised the benefits of using direct marketing, such as receiving direct response from customers and gaining a better customer relation. The growth within direct marketing means that traditional mass marketing today face harder competition than ever.
This thesis examines and look in to three well recognised Swedish companies use of direct marketing. Our main purpose is to establish how companies spend their marketing budget between direct marketing and traditional marketing activities. In this purspose, we aim to look in to the companies marketing activities over the last few years. In relation to this, we also want to establish the main reasons for why companies has increased their direct marketing.