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Lacoursière-Roussel, Anaïs. "Testing propagule pressure theory: maritime transport & invasion by fouling species". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117064.
Pełny tekst źródłaL'introduction des salissures biologiques exotiques a sévèrement perturbé les écosystèmes marins. La théorie suggère qu'un apport de propagules élevé augmente le risque d'envahissement. C'est ainsi que les recherches se sont concentrées à évaluer la probabilité que les navires commerciaux et les petites embarcations transportent des espèces exotiques. Malgré son importance, peu d'études empiriques supportent l'effet de l'apport de propagules sur le succès d'envahissement. Pour les salissures biologiques marines, l'incertitude entre les vecteurs et les voies de transports entrave particulièrement notre capacité à calculer l'apport de propagules entrant par les voies maritimes, limitant ainsi notre compréhension du succès d'envahissement. L'objectif de ma thèse est d'apporter une meilleure compréhension de la relation entre l'apport de propagules provenant du transport maritime et la distribution spatiale des salissures exotiques. À partir de données empiriques, (1) j'ai déterminé l'importance relative des caractéristiques des bateaux de plaisance et l'exposition des propagules environnantes sur la probabilité de la colonisation des coques, (2) j'ai démontré le rôle respectif des navires et des plaisanciers dans le processus d'invasion et (3) j'ai décrit la relation entre l'apport de propagules et la diversité des populations et des communautés. Bien que les bateaux de la côte est du Canada sont moins colonisés que les bateaux de la Nouvelle-Zélande, la propagation des salissures exotiques pourrait être facilitée au Canada par un plus grand trafic entre les marinas. L'exposition aux propagules environnantes prédit davantage l'encrassement biologique des coques que les caractéristiques des bateaux. La génétique des populations de l'ascidie Botryllus schlosseri suggère qu'il y a eu plusieurs introductions dans les ports de la côte est du Canada. Facilité par les plaisanciers, le tunicier s'est ensuite dispersé progressivement autour de ceux-ci. Les indices de diversité soutiennent la relation positive entre l'apport de propagules et le succès d'envahissement et cela autant au niveau des communautés (c.-à-d. la richesse inter-spécifique) qu'au niveau des populations (c.-à-d. diversité génétique). La diversité est significativement corrélée au nombre d'arrivées des navires, mais n'est pas corrélée au nombre de déchargements et au volume de l'eau de lest. Ces relations suggèrent une plus grande importance de l'encrassement des navires que l'eau de lest comme voie d'introduction des salissures exotiques. Cette thèse démontre que les petits bateaux et les navires influencent grandement les processus d'invasions des salissures biologiques des régions côtières du Canada. Cette recherche souligne également que les modèles de propagation des salissures exotiques devraient fonder leurs prémisses sur l'exposition des propagules locales, les caractéristiques des bateaux et l'activité nautique régionale. La nécessité de décrire avec précision les relations entre l'apport de propagules et le succès d'envahissement est l'un des grands défis écologiques afin d'améliorer notre compréhension sur les changements rapides actuellement observés dans nos écosystèmes marins.
Lo, Veronica Bethany Pui Gwun. "Underwater aliens : quantifying propagule pressure of aquatic invasive species in Canadian shipping ports". Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/13696.
Pełny tekst źródłaTaylor, Laura Alayna. "Propagule Pressure and Disturbance Drive the Spread of an Invasive Grass, Brachypodium sylvaticum". PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/41.
Pełny tekst źródłaDressler, Michael D. "Uncovering the Role of Propagule Pressure in Determining Establishment Success Using a Synthetic Biology Approach". Thesis, NSUWorks, 2018. https://nsuworks.nova.edu/occ_stuetd/491.
Pełny tekst źródłaGertzen, Erin. "Assessing the relationship between propagule pressure and probability of establishment for the aquatic invader «Bythotrephes longimanus» using two complementary approaches". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86585.
Pełny tekst źródłaL'estimation de la probabilité d'établissement d'espèces invasives est un élément important pour la gestion de leur dispersion. Dans cette thèse, je présente deux approches pour estimer la probabilité d'établissement de Bythotrephes longimanus, un cladocère prédateur qui se disperse à travers des lacs en Ontario et des états Américains avoisinants. D'abord, je développe un modèle basé sur les procédés pour évaluer la probabilité d'établissement de B. longimanus au fil du temps dans un bassin versant. J'emploie des métriques de pression de propagules en provenance de disséminations anthropiques et naturelles afin d'estimer leur dispersion, et j'étends le modèle pour incorporer le manque de certaines informations spatiales et temporelles concernant l'état d'invasion des lacs. Mes résultats indiquent que la circulation de bateaux de plaisance est le vecteur dominant de dispersion et que la majorité du risque d'invasion des lacs est dû à plusieurs points statiques d'invasion - les cinq lacs les plus grands du système. J'étudie ensuite la probabilité d'établissement empiriquement. Je mène une expérience contrôlée afin de suivre des populations récemment introduites de B. longimanus au cours de leur cycle de vie et je cherche des facteurs liées a la dynamique du début d'invasion qui pourraient affecter la façon dont laquelle les pressions de propagules et le succès d'établissement sont reliés. Ceci inclut la stochasticité démographique et environnementale, des opportunités saisonnières où l'établissement est possible, ainsi que la diminution des opportunités et les effets Allee pendant la reproduction sexuelle. Mes résultats suggèrent que l'établissement de B. longimanus est limité aux effets Allee ou aux diminutions d'opportunités pendant reproduction sexuelle pour les populations introduites en doses bases et que les effets Allee se renforcent pendant l'automne. De plus, la probabilité d'établissement est re
Williams, Moira Caroline. "The ecological impacts of invasive Pinus radiata in eucalypt vegetation: pattern and process". School of Biological Sciences. University of Sydney, 2008. http://hdl.handle.net/2123/2761.
Pełny tekst źródłaEarly recognition of plant invaders is key to their successful management. Yet knowledge of the ecological impacts of species before they become widespread is poor. This thesis examines the ecology of invasive Pinus radiata, a species which is known to spread from introduced plantings in Australia but is currently a low profile invader. Pinus invasions are considered major ecological problems in New Zealand and South Africa where wildlings are beginning to dominate natural areas and suppress native vegetation. Invasion success elsewhere and the large softwood estate in Australia suggest that pines may begin to dominate native eucalypt forests bordering large commercial plantations. This research focused on three components of impact of P. radiata; extent, abundance and effect per individual. The borders of 29 P. radiata plantations in NSW were surveyed in order to quantify the current level of invasion and to identify factors facilitating pine spread. Of particular interest was the role of propagule pressure, vegetation type and fire in the invasion process. The area of land in NSW currently invaded by P. radiata was estimated at almost 4 500 ha, although this is likely to be an underestimate due to an inability to detect wildlings (self-sown pines) at long distances from the plantation. Twenty six of the 29 plantations produced wild pines, however most of the sites are in the very early stages of invasion. Noticeable wildling populations were recorded at nine sites indicating that P. radiata is capable of establishing within native vegetation. Pine spread was most severe in the world heritage listed Blue Mountains region where pine densities reached up to 2000 per hectare in areas adjacent to the plantation and isolated pines were recorded up to 4 km from the source. The presence of isolated pines within intact native vegetation suggests that disturbance is not required for pine establishment in forested environments. Furthermore, high pine emergence and survival rates in eucalypt woodland and evidence of self reproduction by wildlings suggest that in the absence of adequate control measures pines may become established invaders in the Australian landscape. While low levels of current invasion at many sites hindered the ability to examine the factors facilitating invasion some variables that appear to be driving pine success were identified. At the landscape scale plantation size and residence time were significant predictors of the level of invasion at a site. Areas of native vegetation vi adjacent to plantations less than 40 years experienced very low levels of invasion suggesting a lag period between plantation establishment and invasion. However, pines with diameters up to 60 cm were observed growing adjacent to plantations younger than 40 years implying that the first colonisers are capable of establishing soon after plantation trees become reproductive. Propagule pressure was also found to have a strong influence on invasion success on a smaller scale manifesting in a significant positive relationship between the age of a plantation compartment and the likelihood of invasion. A negative relationship between plantation size and level of invasion was a surprising result and was influenced by just two large sites that happened to be located in areas of high rainfall. All sites receiving more than 1300 mm annual rainfall experienced low levels of invasion suggesting that this is a limiting factor for pine spread in NSW. There were significant differences in the level of invasion between vegetation types implying that some communities are more susceptible to invasion. Patterns of spread confirmed ideas regarding the facilitative effect of disturbance in the invasion process and the resistance of wet sclerophyll forest to invasion in Australia. An absence of wildlings in cleared land and areas of remnant bushland was attributed to high levels of grazing pressure. Wind direction did not appear to influence the distribution of pines close to the plantation, but evidence of long distance wind dispersal of pines was provided by an investigation of pine spread from the air at one site where large pines were found growing 10 km downwind from a mature plantation. Fire was found to have both a positive and negative influence on the invasion process. High intensity wildfires are capable of destroying large pines with diameters exceeding 50 cm. However, fire can stimulate seed release from cones resulting in large post-fire recruitment pulses. Seedling densities of up to 3050 per hectare were recorded almost 3 years after wildfire, suggesting that follow up control prior to recruits reaching coning age, i.e. within 5 years, would be beneficial. Surveys of wildling pines exposed to low intensity hazard reduction burns suggest that the majority of pines greater than 3 m in height and with a diameter of more than 10 cm will survive the fire. Low intensity prescribed fires that are carried out after pines have reached this size will fail to control wildling populations. To examine the influence of P. radiata once it has established in the native community this study focused on two mechanisms of impact, the addition of pine litter and increased shade due to an increase in canopy cover. Collection of pine litterfall vii within an invaded eucalypt woodland over a 2 year period recorded rates of up to 1400 kg/ha/year in the most heavily invaded area with a pine basal area of 11.3m2/ha. More than 70 % of pine litter fell directly below the pine canopy suggesting that the most severe litter effects will be limited to these areas. Glasshouse and field experiments were conducted to examine the influence of this increased litter load on the emergence of P. radiata and two native species. Recruitment of native plant species was impeded by litter levels of 6000 kg/ha, the equivalent of approximately 4 years of pine litterfall. Both P. radiata and the two natives responded similarly to pine and eucalypt litter suggesting the two litter types are influencing the recruitment phase equally. However, where pines are added to the system, increased litterfall rates could potentially result in the doubling of the litter load and hence a greater barrier to seedling establishment. Pine invaded eucalypt woodlands are also subjected to three fold increases in canopy cover. Trends in reduced emergence of native species under a pine canopy suggest that the addition of pines to eucalypt forests is likely to have a negative influence on native recruitment and may result in a shift towards a shade tolerant community. However, reversal of trends in emergence below pine canopy between seasons implies that quantifying invasion impacts requires a consideration of temporal variation. Increased levels of disturbance, forest fragmentation and an increasing pine estate are likely to lead to the infestation of new areas. Furthermore the lag phase associated with pine spread means that even if no new plantations are established the number of invasion events will increase. This study has identified a number of risk factors that can be used to guide plantation establishment and the management of invasion events. Minimising disturbance at plantation borders and increasing the ‘no planting’ zone will help to reduce the impacts of pines. Where possible new plantations should be established upwind of cleared land or at least, wet sclerophyll forest. Frequent monitoring of the borders of plantations yet to source invasions, particularly those greater than 40 years of age, will help identify problem areas before control becomes difficult and costly. Maps of the 29 plantations marked with areas of pine infestation will help prioritise sites for control and provide base level knowledge for future monitoring of pine spread. Stringent legislation that binds plantation managers to control wildlings beyond their boundaries is critical for the effective management of pine invasions. With infinite numbers of invaders and limited funds to dedicate to their control, a method of triaging species for management is critical. This is particularly difficult viii when information is typically biased towards invaders that are already widespread. By focussing on the ecological impacts of invaders it becomes possible to rank species on the basis of the threat they pose to native communities. Ecological research is capable of providing the knowledge to quantify invasion impacts and must remain at the centre of policy decisions.
Humphrey, Donald B. "Characterizing ballast water as a vector for nonindigenous zooplankton transport". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2391.
Pełny tekst źródłaFernandes, Rogerio Taygra Vasconcelos. "Padrões e processos de diferenciação taxonômica da fauna de peixes de uma ecoregião da América do Sul". Universidade Federal Rural do Semi-Árido, 2013. http://bdtd.ufersa.edu.br:80/tede/handle/tede/700.
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Here, we quantified the patterns of change in the similarity of the fish fauna of the Upper Paraná ecoregion, caused by the introduction of non-native species and anthropogenic factors, such as the construction of dams and the elimination of a biogeographic barrier. Additionally, we evaluated the importance of changes in rates of turnover and richness species in homogenization/differentiation dynamics. For the study, we mapped the spatial distribution of fish species through occurrence data georeferenced of Brazilian zoological museums. To evaluate temporal changes in the composition of the fish fauna, the data with the distribution of the species were divided into two periods: historical period composed entirely of native species, and the contemporary period, consisting of historical fauna plus non-native species. Changes in similarity patterns between fish assemblages were quantified using the Jaccard dissimilarity index to the historical and contemporary periods. To evaluate the influence of the non-native richness species, number of dam and distance to the Itaipu Dam on changes of similarity, we performed simple and partial Mantel tests. The results showed that the fish fauna has become more dissimilar over time, due to increases in turnover rates and addition of species. Furthermore, factors related to the heterogeneity of the basins and propagules pressure after removal of a biogeographical barrier has determined the patterns of changes in the similarity of the fish fauna
Nesse estudo foram quantificados os padrões de mudança na similaridade da fauna de peixes da ecoregião do alto Paraná, produzidas pela introdução de espécies não-nativas e de fatores antropogênicos, como a construção de barragens e a eliminação de uma barreira biogeográfica. Adicionalmente, foi avaliada a importância de mudanças nas taxas de turnover e de riqueza nas mudanças de similaridade das assembleias de peixes. Para realizar o estudo, a distribuição espacial de espécies de peixes de dez bacias de drenagem do alto Paraná foi mapeada através de dados de ocorrência geo-espacializados tombados em museus zoológicos de instituições brasileiras. Para avaliar as mudanças temporais na composição da fauna de peixes, os dados com as distribuição das espécies foi divido em dois períodos: período histórico, composto somente por espécies nativas, e período contemporâneo, composto por espécies nativas mais não-nativas. Os padrões de similaridade entre as assembleias de peixes para os períodos histórico e contemporâneo foram quantificados através do índice de dissimilaridade de Jaccard. As mudanças na similaridade entre assembleias foi calculada através da diferença entre as similaridades contemporâneas e históricas. Para avaliar os efeitos da riqueza de espécies não-nativas, número de barragens e área das bacias, e a distância das bacias até a barragem de Itaipu foram utilizados testes de Mantel simples e parciais. Os resultados demostraram que a fauna de peixes tem se tornado mais dissimilar ao longo do tempo, em função de aumentos nas taxas de turnover e de adição de espécies. Além disso, fatores relacionados à heterogeneidade das bacias e da pressão de propágulos após a eliminação de uma barreira biogeográfica tem determinado os padrões de mudanças na similaridade da fauna de peixes
2017-05-18
Henrique, Rafael dos Santos. "Ecologia do movimento da rã-manteiga (Leptodactylus latrans) e da rã-touro (Lithobates catesbeianus)". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/41/41133/tde-18042017-103924/.
Pełny tekst źródłaThe ability of animals to move plays an important role in individual fitness, gene flow, population regulation, metapopulation dynamics and long-term persistence of species. The aim of this study was to understand aspects related to the movement ecology of the Butter Frog (Leptadactylus latrans) and the Bullfrog (Lithobates catesbeianus). We collected movement data by radio tracking individuals of both species. Some of the most important results obtained were: (1) the mean home range of L. latrans is 2034.2 m2; (2) increasing body size increases home range size in anurans; (3) individuals of L. latrans are more likely to move larger distances in dark, rainy and warm nights; (4) the increase in propagule pressure does not reflect an increase in the probability of geographical spread of a given population of L. catesbeianus. Understanding how amphibians move and use the space in nature is fundamental for the understanding of basic ecological and evolutionary processes related to life history of the species. Moreover, this knowledge is a useful tool to establish biologically meaningful conservation boundary areas to threatened species. Yet, understanding how invasive species move in nature is one of the first steps to population control and to block the spread of geographical distribution of exotic species
Firmat, Cyril. "Hybridation et goulots d'étranglements induits par l'activité humaine : génétique des populations, morphométrie et parasitologie appliquées au tilapia envahi et envahissant Oreochromis mossambicus (Teleostei, Cichlidae)". Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00879836.
Pełny tekst źródłaCohen, Gabriel Jorgewich. "Genética de populações aplicada à biologia da invasão: um panorama da invasão da rã-touro (Lithobates catesbeianus)". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/41/41133/tde-26062018-091821/.
Pełny tekst źródłaBiological invasions play an increasingly important role in environmental policies as invasive species represent a growing impact in new environments where they are introduced, potentially causing large natural and financial problems. Studies in the field of invasion biology are extremely necessary to remedy and prevent new introductions. Among the methodologies applied to the study of biological invasions, population genetics presents several useful tools to answer relevant questions in efforts to control invasive species. In the present work we used molecular resources applied to the genetics of populations of the American Bullfrog (Lithobates catesbeianus), the most widespread invasive amphibian on the planet. Through this study it was possible to understand more about the genetic structure of the invasive populations in Brazil and in the world, and its history of invasion and its native population of origin. Understanding and contextualizing the characteristics and motives that lead to the success of a biological invasion is important for pest control efforts and to prevent other invaders from focusing on new environments. This work has raised new knowledge that can and should be used in policies to combat Bullfrog invasion
Velasquez, Eleanor. "Unique island habitats: A comparison of community assembly in marine and terrestrial contexts". Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/124649/2/Eleanor%20Velasquez%20Thesis.pdf.
Pełny tekst źródłaBanks, Christopher Mark. "New Zealand Calanoid Copepod Invasions: Has Artificial Lake Construction Facilitated Invasions, and are our Coastal Waters Uninvaded?" The University of Waikato, 2007. http://hdl.handle.net/10289/2269.
Pełny tekst źródłaLilley, Patrick Ledford. "Determinants of native and exotic plant species diversity and composition in remnant oak savannas on southeastern Vancouver Island". Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/243.
Pełny tekst źródłaMeffin, 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.
Pełny tekst źródłaSchimanski, Kate Bridget. "The importance of selective filters on vessel biofouling invasion processes". Thesis, University of Canterbury. School of Biological Sciences, 2015. http://hdl.handle.net/10092/11299.
Pełny tekst źródłaDe, Jong Gabriel Louis. "Past and present effects of propagule pressure on spatial distributions of non-native woody plants in central Texas". Thesis, 2014. http://hdl.handle.net/2152/26485.
Pełny tekst źródłatext
Maier, Caroline Alexandra. "The influence of propagule pressure on community diversity and invasion success in an aquatic protist system". 2010. http://hdl.rutgers.edu/1782.2/rucore10002600001.ETD.000052190.
Pełny tekst źródłaLee, Chih-Chi, i 李志琦. "The role of propagule pressure and genetic diversity in successful invasion of the red imported fire ant (Solenopsis invicta) in Taiwan". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/18577636452509221206.
Pełny tekst źródła國立臺灣大學
昆蟲學研究所
99
Genetic diversity is one of the key determinants for species’ survival and evolution. From the conservation biology perspective, a small population is prone to extinction by inbreeding depression or accumulation of deleterious mutations. Invasive species, however, are generally successful in introduced ranges despite loss of genetic diversity due to small founder population sizes, which gives rise to a paradox between invasion and conservation biology in term of genetic diversity. Social insects, such as ants, wasps, and termites, represent a highly successful group of invasive species not only because their small founder population sizes often lack immediately recognizable signature but also their great dispersal power, high reproductive rate and the competitive ability of “super individuals”. One of the notorious ant invaders, the red imported fire ant (Solenopsis invicta), originating from South America, has been accidentally introduced into the USA, Australia, Taiwan and China. Invasions by fire ants in these areas provide an excellent framework to investigate the factors contributing to the successful establishment of social insects especially since this species utilizes a single locus complementary sex determination (sl-CSD) system. Theoretically, the genetic load is predicted to be much more profound for S. invicta due to the mass production of sterile diploid males imposed by loss of genetic diversity. This study therefore aimed to determine how fire ants overcome such a disadvantage using population genetic approaches. An assessment of genetic variation at 12 microsatellite loci in 120 fire ant colonies in northern Taiwan (Taoyuan) revealed that Taoyuan was colonized by ants on a minimum of two occasions. Furthermore, estimates of genetic diversity at the CSD locus by calculating the proportion of match matings (queens mated with males harboring identical CSD allele) do not differ significantly between fire ant populations in Taiwan and the putative source, the USA, suggesting that the successful invasion of fire ants is likely attributable to adequate genetic diversity maintained by larger propagule number (e.g, multiple invasions). In summary, this study not only highlights that cryptic invasions might be undetected until the deep genetic structure of focal populations has been revealed but also signifies the importance of genetic diversity in shaping the invasion success of fire ants.
Kennedy, Bradley. "The new invasive Odontites serotina: impacts, responses and predictive model". 2012. http://hdl.handle.net/1993/5031.
Pełny tekst źródłaArpin, Pascal. "Étude comparative des propagules extraracinaires et intraracinaires du champignon mycorhizien Glomus irregulare". Thèse, 2012. http://hdl.handle.net/1866/8921.
Pełny tekst źródłaSpore germination is an essential developmental stage in the life cycle of many filamentous fungi. Arbuscular mycorrhizal fungi (AMF) form a number of different infectious propagules that increase their potential to colonize roots. Among them are extraradical and intraradical spores. The spore cell wall plays a major role in the survival of these propagules by being a physical and osmotic barrier. Because a cell can make considerable adjustments to the composition and structure of its wall in response to environmental conditions, it is possible that intraradical and extraradical spore walls show different mechanical and osmotic properties affecting their survival and germination. However, in contrast to the knowledge on the genetics and molecular composition of AMF cell wall, little is known about its mechanical properties. Information on the germination of AMF under hypertonic conditions is scarce, and experimental designs and methodologies have generally not allowed the direct effects of high external osmotic pressure on fungal germination to be separated from plant-mediated effects. This study had the goal to address two important sets of questions regarding the behavior of mycorrhizal spores. We first determined the relationship between cell wall composition, structure and mechanical properties of the model fungus Glomus irregulare. Micro-indentation was used to quantitatively measure the cell wall mechanical properties. Cell wall composition (chitin and glomalin content) was studied by immunofluorescence whereas optical microscopy was used to measure the cell wall thickness. Glomalin local density and wall thickness were both significantly higher for extraradical spore walls while chitin local density and rigidity were unaffected by origin of spores. High variability in results prevented us from identifying a primary factor responsible for overall wall strength during compression. Decreases of chitin and glomalin concentrations were correlated to the development of the fungal wall throughout its life-cycle. There was also differential association within the wall layers: The chitin and glomalin polymers were localized mostly in the outer and inner walls, respectively. In the second part of our work, we explored the direct effects of fertilizers, in relation to their water activity (aw), on spore germination and cellular turgor pressure. Spores were exposed to three fertilizers with different aw and spore germination and cytorrhysis of spores were assessed after different times of incubation. Water activities of the fertilizers were used as indicators of their osmotic pressures. Osmotic shock exposure of the Glomus irregulare spores to fertilizers at aw values between 0.982 and 0.882 caused gradual changes in cytorrhysis and germination. With the increase of external turgor pressure, cytorrhysis increased while the rate of germination decreased. These effects were most pronounced at high nutrient concentrations. The present investigation, while likely representing a significant step forward in understanding the mechanical and osmotic properties of AMF spores, also confirms that they might depend on many, as yet unidentified factors. Future research should examine differences in the physiology to discern reasons for such differences in spore properties.