Literatura académica sobre el tema "Propagule pressure"
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Artículos de revistas sobre el tema "Propagule pressure"
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Moulton, Michael P. y Wendell P. Cropper. "Propagule pressure does not consistently predict the outcomes of exotic bird introductions". PeerJ 7 (11 de septiembre de 2019): e7637. http://dx.doi.org/10.7717/peerj.7637.
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Some have argued that the role of propagule pressure in explaining the outcomes of bird introductions is well-supported by the historical record. Here, we show that the data from a large published database (including 832 records with propagule information) do not support the conclusion that propagule pressure is the primary determinant of introduction success in birds. A few compendia of historical reports have been widely used to evaluate introduction success, typically by combining data from numerous species and introduction locations. Very few taxa, other than birds, have usable spatially explicit records of introductions over time. This availability of data inflates the perceived importance of bird analyses for addressing factors related to invasion success. The available data allow limited testing of taxonomic and site-level factors of introduction outcomes. We did find significant differences in effort and success probabilities among avian orders and across highly aggregated spatial regions. As a test of a standard and logical expectation of the propagule pressure hypothesis, we concentrated on introductions with the smallest propagules, because it is for these the hypothesis is most likely to be correct. We analyzed the effect of numbers released in small propagules (two through 10) for 227 releases. Weighted linear regression indicated no significant effect of propagule size for this range of release size. In fact, the mean success rate of 28% for propagules of 2–10 isn’t significantly different than that of 34% for propagules of 11–100. Following the example of previous analyses, we expanded the statistical test of propagule pressure to include the full range of release numbers. No significant support for the propagule pressure hypothesis was found using logistic regression with either logit or complementary log-log link functions.
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Wittmann, Meike J., Dirk Metzler, Wilfried Gabriel y Jonathan M. Jeschke. "Decomposing propagule pressure: the effects of propagule size and propagule frequency on invasion success". Oikos 123, n.º 4 (6 de febrero de 2014): 441–50. http://dx.doi.org/10.1111/j.1600-0706.2013.01025.x.
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Smyth, Eric R. B. y D. Andrew R. Drake. "The role of propagule pressure and environmental factors on the establishment of a large invasive cyprinid: black carp in the Laurentian Great Lakes basin". Canadian Journal of Fisheries and Aquatic Sciences 79, n.º 1 (enero de 2022): 6–20. http://dx.doi.org/10.1139/cjfas-2020-0187.
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Understanding the factors underlying species establishment is critical for the management of invasive fishes, yet the roles of propagule pressure and environmental factors are infrequently quantified in joint models. We estimated the establishment likelihood of the invasive black carp (Mylopharyngodon piceus) by examining the relative influence of propagule pressure (introduction size and age structure) and environmental factors (temperature-driven young-of-year [YOY] overwinter survival, adult survival, age at maturity, and longevity). Simulations demonstrated that both propagule pressure and environmental factors can act as non-linear bottlenecks to establishment. When the model was applied to 12 Great Lakes tributaries and nearshore areas, black carp establishment was probable with sufficient propagules and under most environmental conditions (median p = 0.21–0.73, 0.70–1.00, and 0.46–0.97 for 100 pairs of age 4, age 9, and age 16 fish, respectively), except for YOY (p < 0.01). Our analysis is one of the few studies to examine the relative role of propagule pressure and environmental conditions on establishment, indicating that both factors can lead to establishment failure independently or concurrently within an ecosystem.
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Briski, Elizabeta, Sarah A. Bailey, Oscar Casas-Monroy, Claudio DiBacco, Irena Kaczmarska, Colin Levings, Michael L. MacGillivary et al. "Relationship between propagule pressure and colonization pressure in invasion ecology: a test with ships' ballast". Proceedings of the Royal Society B: Biological Sciences 279, n.º 1740 (28 de marzo de 2012): 2990–97. http://dx.doi.org/10.1098/rspb.2011.2671.
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Increasing empirical evidence indicates the number of released individuals (i.e. propagule pressure) and number of released species (i.e. colonization pressure) are key determinants of the number of species that successfully invade new habitats. In view of these relationships, and the possibility that ships transport whole communities of organisms, we collected 333 ballast water and sediment samples to investigate the relationship between propagule and colonization pressure for a variety of diverse taxonomic groups (diatoms, dinoflagellates and invertebrates). We also reviewed the scientific literature to compare the number of species transported by ships to those reported in nature. Here, we show that even though ships transport nearly entire local communities, a strong relationship between propagule and colonization pressure exists only for dinoflagellates. Our study provides evidence that colonization pressure of invertebrates and diatoms may fluctuate widely irrespective of propagule pressure. We suggest that the lack of correspondence is explained by reduced uptake of invertebrates into the transport vector and the sensitivity of invertebrates and diatoms to selective pressures during transportation. Selection during transportation is initially evident through decreases in propagule pressure, followed by decreased colonization pressure in the most sensitive taxa.
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Levin, Donald A. "Ancient Dispersals, Propagule Pressure, and Species Selection in Flowering Plants". Systematic Botany 31, n.º 3 (1 de julio de 2006): 443–48. http://dx.doi.org/10.1600/036364406778388692.
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The importance of ancient long-distance migrations in shaping the geographical structure of genera and families is becoming ever more apparent. The long-distance immigrants were not random samples of their floras, but had attributes which made them prime candidates for the intercontinental sweepstakes. High propagule dispersability was one such trait. I propose that these invasive species also must have produced large numbers of propagules across their ranges, by virtue of large population numbers and sizes. They probably were widespread, major elements in their floras. These ideas are supported by the fact that propagule pressure is a prime determinant of a contemporary species' invasion potential, as is the size of its native geographical distribution. I propose that highly dispersable and propagule-rich lineages are likely to have high speciation rates, because access to new regions affords opportunities for ecological and geographical speciation. These lineages also may persist longer, being more broadly distributed in space. The evolutionary advantage of these lineages extends to periods of climatic change.
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Drake, John M., Peter Baggenstos y David M. Lodge. "Propagule pressure and persistence in experimental populations". Biology Letters 1, n.º 4 (31 de agosto de 2005): 480–83. http://dx.doi.org/10.1098/rsbl.2005.0375.
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Average inoculum size and number of introductions are known to have positive effects on population persistence. However, whether these factors affect persistence independently or interact is unknown. We conducted a two-factor experiment in which 112 populations of parthenogenetic Daphnia magna were maintained for 41 days to study effects of inoculum size and introduction frequency on: (i) population growth, (ii) population persistence and (iii) time-to-extinction. We found that the interaction of inoculum size and introduction frequency—the immigration rate—affected all three dependent variables, while population growth was additionally affected by introduction frequency. We conclude that for this system the most important aspect of propagule pressure is immigration rate, with relatively minor additional effects of introduction frequency and negligible effects of inoculum size.
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Seebens, Hanno, Elizabeta Briski, Sara Ghabooli, Tamara Shiganova, Hugh J. MacIsaac y Bernd Blasius. "Non-native species spread in a complex network: the interaction of global transport and local population dynamics determines invasion success". Proceedings of the Royal Society B: Biological Sciences 286, n.º 1901 (24 de abril de 2019): 20190036. http://dx.doi.org/10.1098/rspb.2019.0036.
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The number of released individuals, which is a component of propagule pressure, is considered to be a major driver for the establishment success of non-native species. However, propagule pressure is often assumed to result from single or few release events, which does not necessarily apply to the frequent releases of invertebrates or other taxa through global transport. For instance, the high intensity of global shipping may result in frequent releases of large numbers of individuals, and the complexity of shipping dynamics impedes predictions of invasion dynamics. Here, we present a mathematical model for the spread of planktonic organisms by global shipping, using the history of movements by 33 566 ships among 1477 ports to simulate population dynamics for the comb jelly Mnemiopsis leidyi as a case study. The degree of propagule pressure at one site resulted from the coincident arrival of individuals from other sites with native or non-native populations. Key to sequential spread in European waters was a readily available source of propagules and a suitable recipient environment. These propagules were derived from previously introduced ‘bridgehead’ populations supplemented with those from native sources. Invasion success is therefore determined by the complex interaction of global shipping and local population dynamics. The general findings probably hold true for the spread of species in other complex systems, such as insects or plant seeds exchanged via commercial trade or transport.
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Acosta, Francisco, Richard M. Zamor, Fares Z. Najar, Bruce A. Roe y K. David Hambright. "Dynamics of an experimental microbial invasion". Proceedings of the National Academy of Sciences 112, n.º 37 (31 de agosto de 2015): 11594–99. http://dx.doi.org/10.1073/pnas.1505204112.
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The ecological dynamics underlying species invasions have been a major focus of research in macroorganisms for the last five decades. However, we still know little about the processes behind invasion by unicellular organisms. To expand our knowledge of microbial invasions, we studied the roles of propagule pressure, nutrient supply, and biotic resistance in the invasion success of a freshwater invasive alga, Prymnesium parvum, using microcosms containing natural freshwater microbial assemblages. Microcosms were subjected to a factorial design with two levels of nutrient-induced diversity and three levels of propagule pressure, and incubated for 7 d, during which P. parvum densities and microbial community composition were tracked. Successful invasion occurred in microcosms receiving high propagule pressure whereas nutrients or community diversity played no role in invasion success. Invaded communities experienced distinctive changes in composition compared with communities where the invasion was unsuccessful. Successfully invaded microbial communities had an increased abundance of fungi and ciliates, and decreased abundances of diatoms and cercozoans. Many of these changes mirrored the microbial community changes detected during a natural P. parvum bloom in the source system. This role of propagule pressure is particularly relevant for P. parvum in the reservoir-dominated southern United States because this species can form large, sustained blooms that can generate intense propagule pressures for downstream sites. Human impact and global climate change are currently causing widespread environmental changes in most southern US freshwater systems that may facilitate P. parvum establishment and, when coupled with strong propagule pressure, could put many more systems at risk for invasion.
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Gertzen, Erin, Oriana Familiar y Brian Leung. "Quantifying invasion pathways: fish introductions from the aquarium trade". Canadian Journal of Fisheries and Aquatic Sciences 65, n.º 7 (julio de 2008): 1265–73. http://dx.doi.org/10.1139/f08-056.
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Introduced species can cause economic and environmental harm. Researchers have developed risk assessment models for exotic species based on biological characteristics. However, few have quantified propagule pressure despite its relevance for establishment. Both are needed to identify invasion risk. We focused on fishes introduced via the aquarium trade, because this pathway transports thousands of species throughout the world. We developed an approach to estimate propagule pressure by (i) identifying and quantifying aquarium fishes sold, (ii) determining fish owner behavior and disposal practices, and (iii) quantifying uncertainty. We used the St. Lawrence Seaway as our model system. Only one nonestablished species ( Tanichthys albonubes , 117 per year) had the propagule pressure and environmental tolerances to likely invade this region. However, overall, more than 10 000 fishes were released annually from Montréal (Quebec, Canada) alone. The implication of the observed propagule pressures is that the aquarium trade should be a very important pathway in other warmer habitats and should be explicitly assessed. Knowledge of the numbers introduced of each species will be useful for population models to estimate the probability of establishment.
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Levin, Donald A. "Propagule pressure and the establishment of emergent polyploid populations". Annals of Botany 127, n.º 1 (27 de octubre de 2020): 1–5. http://dx.doi.org/10.1093/aob/mcaa187.
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Abstract Background Whereas the incidence or rate of polyploid speciation in flowering plants is modest, the production of polyploid individuals within local populations is widespread. Explanations for this disparity primarily have focused on properties or interactions of polyploids that limit their persistence. Hypothesis The emergence of local polyploid populations within diploid populations is similar to the arrival of invasive species at new, suitable sites, with the exception that polyploids suffer interference from their progenitor(s). The most consistent predictor of successful colonization by invasive plants is propagule pressure, i.e. the number of seeds introduced. Therefore, insufficient propagule pressure, i.e. the formation of polyploid seeds within diploid populations, ostensibly is a prime factor limiting the establishment of newly emergent polyploids within local populations. Increasing propagule number reduces the effects of genetic, environmental and demographic stochasticity, which thwart population survival. As with invasive species, insufficient seed production within polyploid populations limits seed export, and thus reduces the chance of polyploid expansion. Conclusion The extent to which propagule pressure limits the establishment of local polyploid populations remains to be determined, because we know so little. The numbers of auto- or allopolyploid seed in diploid populations rarely have been ascertained, as have the numbers of newly emergent polyploid plants within diploid populations. Moreover, seed production by these polyploids has yet to be assessed.
Tesis sobre el tema "Propagule pressure"
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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.
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Introductions of exotic fouling species have severely disrupted marine ecosystems. Theory suggests that high propagule pressure increases the probability of successful establishment. Likewise, empirical studies have shown the importance of ships and boats for transporting exotic species. However, few empirical studies have demonstrated the effect of propagule pressure on invasion success. For marine fouling species, uncertainty about vectors and pathways further impedes our ability to calculate propagule pressure and to understand establishment success. My goal was to better understand the links between propagule pressure from maritime activities and the spatial distribution of exotic fouling species. Using empirical data, I (1) determined the importance of boat characteristics and propagule exposure on boat fouling, (2) demonstrated the roles of commercial shipping and recreational boating in the invasion process, and (3) tested the effect of propagule pressure on population and community diversity. Although boats on the east coast of Canada were less fouled than New Zealand boats, boat-mediated spread may be facilitated in Canada by greater movement of boats among marinas than in New Zealand. Propagule exposure better predicted boat fouling than did boat characteristics. The spatial genetic structure of the colonial tunicate, Botryllus schlosseri, suggests that ships have frequently introduced it to the east coast of Canada and that secondary spread occurs gradually around individual ports, facilitated by recreational boating. The diversity of invasive species within commercial ports is positively related to propagule pressure and invasion success at both community (i.e. inter-specific richness) and population levels (i.e. genetic diversity). Diversity was significantly correlated to the numbers of ship arrivals but not to ballast water discharge events or the volume of ballast water discharged. This suggests that hull biofouling is a more important pathway than ballast water for exotic fouling species. Both boats and ships have influenced the invasion process of fouling species in Canadian coastal areas. The research also underlines the point that predictive models for the spread of biofouling species should be based on regional boating patterns, boating characteristics, and local propagule exposure. Defining relationships between propagule pressure and invasion success is one of the great challenges to understanding the rapid changes occurring in marine ecosystems.L'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.
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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.
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Increased trading worldwide has created introduction pathways for aquatic invasive species (AIS), particularly through shipping activities. In our research, we used ballast discharge data and estimates of the wetted surface area of vessels to provide preliminary estimates of the potential propagule pressure ballast and hull fouling organisms on Canadian shipping ports from the commercial shipping sector. We compared total wetted surface area, vessel arrivals and ballast discharge across shipping ports and vessel categories in the Atlantic, Great Lakes-St. Lawrence and Pacific shipping regions. Using these potential propagule pressure estimates for ballast organisms, we developed a model, building on that of MacIsaac et al.’s (2002), to characterize the effective propagule pressure of aquatic non-native species to Canadian shipping ports. Our model includes the effects of environmental similarity between destination and source on mortality, which can be considerable. We parameterized the model using recent nationally and regionally collected databases on ship voyages, and abundance surveys yielding mortality rates of several zooplankton species. These empirically derived parameters were used in our model to predict abundances of live individuals after ballast is discharged, with estimates of uncertainty and sensitivity to key assumptions. Our results indicate that for our three shipping regions, aggregate wetted surface area, vessel arrivals, and total ballast discharge were significantly correlated across shipping ports (Spearman’s ρ ranged from 0.57 to 0.87, p<0.05). Correlations between these measures of propagule pressure were more variable and of varying levels of significance across vessel categories (Spearman’s ρ ranged from 0.43 to 0.98). Our modeling results demonstrate that variation in mortality rates across tanks and voyages resulted in high variation in total effective propagule pressure. The variation between tanks and voyages has important implications for the use of mid-ocean exchange as a ballast management method for different ports and species. To our knowledge, our characterization of potential and effective propagule pressure from the commercial shipping sector is the first to be conducted on a nation-wide scale. Our propagule pressure estimates will contribute to future efforts to determine the relationship between the establishment of aquatic invasive species and the environmental similarity between source and discharge areas.
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Taylor, 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.
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The invasibility, or susceptibility of an ecosystem to biological invasion is influenced by changes in biotic and abiotic resistance often due to shifts in disturbance regime. The magnitude of invasive propagule pressure interacts with an ecosystem's invasibility to determine the extent of a biological invasion. I examined how propagule pressure, forest community structure and disturbance interact to influence the invasibility of temperate Pacific Northwest forests by the newly-invasive grass, Brachypodium sylvaticum. My goal was to identify which of these factors is most instrumental in enabling the shift from establishment to population growth in B. sylvaticum at the edge of its expanding range. Both observational and experimental studies were employed to identify the many ecological components of this problem. Ecological sampling methods were used to identify trends in B. sylvaticum habitat preference and signs of habitat disturbance. In addition, an experimental study was performed to test the effects of soil and vegetation disturbance on B. sylvaticum seedling propagation. I found that while soil disturbance did not have a significant effect on seedling propagation, vegetation disturbance was implicated in B. sylvaticum spread. Higher propagule pressure and coniferous forest type were also strong predictors of increased B. sylvaticum seedling propagation and survival within established sites. My study demonstrates how propagule pressure and plant community dynamics interact to shift the invasibility of Pacific Northwest forests and facilitate the transition from establishment to spread in the invasion of B. sylvaticum.
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Dressler, 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.
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The spread of invasive species poses a major ecological and economical threat. Consequently there are ongoing efforts to develop a generalizable mechanism to predict establishment success of non-native species. One proposed mechanism to predict establishment success is propagule pressure, which is defined as the number of individuals introduced at a given time. Although some studies have demonstrated a positive correlation between propagule pressure and establishment success, others have not, and the effect of propagule pressure on establishment success remains unclear. To address this challenge, a strain of bacteria engineered with an Allee effect, a growth dynamic that is often associated with establishing species, was used. The timing between successive introduction events that resulted in establishment success was measured. It was observed that if the time between two introduction events was sufficiently long, growth did not occur. By manipulating the growth rate of the bacteria, it was shown that that the minimal time between the two introduction events that resulted in growth was constrained as growth rate decreased. Moreover, it was concluded that asymmetry in the density of bacteria introduced in the introduction events increased the maximum time between introduction events that resulted in growth. These results help to remedy conflicting data in the literature by identifying conditions where propagule pressure has, and does not have, a positive impact on establishment success. These findings can have major implications in understanding and predicting the unique population dynamics of invasive species.
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Gertzen, 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.
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Estimating the probability of establishment of non-indigenous species is a crucial element in managing their spread. In this thesis, I use two approaches to estimate the probability of establishment of Bythotrephes longimanus, a predatory cladoceran that is invading lakes in Ontario and the surrounding American states. At a watershed level, I develop a vector based model to predict the probability of establishment of B. longimanus over time. I use metrics of propagule pressure from anthropogenic and natural dispersal to estimate spread, and extend the model to incorporate spatial and temporal gaps in knowledge of the invasion status of lakes. I found that recreational boating traffic is the dominant vector of spread and that most risk to lakes is due to static hubs of invasion - the five largest lakes in the watershed. Next, at the scale of a local population introduction, I investigate probability of establishment empirically. I follow B. longimanus populations over their entire life cycle and look for evidence of early invasion dynamics that may affect establishment, including Allee effects, demographic and environmental stochasticity, windows of opportunity and bottlenecks during sexual reproduction. I found that populations introduced at low doses exhibit weak Allee effects during sexual reproduction and that these effects strengthen over the season. Further, probability of establishment is positively related to propagule pressure; however, the relation is highly stochastic. The insights obtained on the characteristics of the relation between propagule pressure and probability of establishment at population and watershed scales can be linked in management plans aimed at slowing the spread of B. longimanus in inland lakes.L'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
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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.
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Doctor of Philosophy (PhD)Early 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.
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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.
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The global movement of aquatic non-indigenous species can have severe ecological, environmental and economic impacts emphasizing the need to identify potential invaders and transport pathways. Initial transport is arguably the most important stage of the invasion process owing to its role in selectively determining potential invasion candidates. This study characterizes a well defined human-mediated dispersal mechanism, ballast water transport, as a vector for the introduction of non-indigenous zooplankton. Ballast water exchange in the open ocean is the most widely adopted practice for reducing the threat of aquatic invasions and is mandatory for most foreign vessels intending to release ballast in Canadian waters. Ships entering Canadian ports are categorized into the following three shipping classes based on current regulations: overseas vessels carrying exchanged ballast water, intra-coastal vessels carrying exchanged ballast water or intra-coastal vessels carrying un-exchanged ballast water. This study characterizes zooplankton communities associated with each of these shipping classes sampled from ports on Canada’s Pacific coast, Atlantic coast and the Great Lakes Basin. Ballast water samples were collected and analyzed from 77 vessels between 2006 - 2007. The ballast water environment was found to be diverse, with over 193 zooplankton taxa, 71 of which were non-indigenous to their receiving environments. Intracoastal vessels containing un-exchanged coastal water transported the greatest density of non-indigenous zooplankton into Canadian ports. Total zooplankton density was found to be negatively correlated with ballast water age The absence of mandatory ballast water exchange and the younger ballast water age of coastal un-exchanged vessels is likely responsible for the higher density of non-indigenous zooplankton in intracoastal un-exchanged vessels. Propagule pressure, invasion history and environmental suitability are all useful in evaluating invasion potential and all suggest that intracoastal un-exchanged vessels pose the greatest invasion threat to Canadian aquatic ecosystems. In conclusion, although the risk of primary introductions from overseas ports may have been reduced through open-ocean exchange of ballast water, secondary introductions from previously invaded ports in North America may be the primary threat to Canadian aquatic ecosystems via this transport vector.
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Fernandes, 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
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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/.
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O movimento dos animais desempenha papel importante na aptidão dos indivíduos, no fluxo gênico, na dinâmica de metapopulações e na persistência, a longo prazo, de espécies em um ambiente. Dessa forma, o objetivo deste estudo foi compreender aspectos relacionados à ecologia do movimento da rã-manteiga (Leptodactylus latrans) e da rã-touro (Lithobates catesbeianus). Para isso, indivíduos de ambas as espécies foram marcados com radiotransmissores e rastreados com o objetivo de coletar informações sobre seus movimentos. Ressaltamos os seguintes resultados deste trabalho: (1) a área de vida média de L. latrans é de 2034,2 m2; (2) com o aumento do tamanho corpóreo de anuros há o aumento do tamanho da área de vida; (3) indivíduos de L. latrans se locomovem mais em noites escuras, chuvosas e quentes; e (4) o aumento da pressão de propágulos não reflete uma maior probabilidade no aumento da distribuição geográfica de uma dada população de L. catesbeianus. Entender os padrões de locomoção dos anfíbios e como utilizam o espaço na natureza é fundamental para o entendimento de processos ecológicos e evolutivos relacionados às histórias de vida das espécies desse grupo. Além disso, esse conhecimento serve como uma ferramenta importante no estabelecimento de limites de áreas de conservação com significado biológico para espécies ameaçadas. Ainda, saber como espécies invasoras se locomovem é um dos primeiros passos para que se tomem medidas de controle populacional e para o bloqueio do avanço da distribuição de espécies exóticasThe 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
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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.
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Les invasions biologiques sont reconnues comme un facteur évolutif important sur une échelle de temps courte. Elles affectent notamment la structure génétique des populations, les patrons d'évolution phénotypique et la richesse des faunes de parasites associées aux populations envahissantes. Cette étude se propose de quantifier les conséquences d'une invasion biologique suivant ces trois niveaux (génétique, phénotypique et parasitologique) en prenant pour exemple le cas du tilapia du Mozambique Oreochromis mossambicus. Ce cichlidé africain présente un statut remarquable en biologie de la conservation puisqu'il est à la fois (i) l'une des espèces les plus envahissantes au monde car dispersée à l'échelle globale au cours du XXème siècle et (ii) une espèce " quasi-menacée " (UICN) sur son aire native (partie du sud-est de l'Afrique) du fait de son hybridation massive avec d'autres Oreochromis sp. introduits. La démarche générale employée ici est de décrire l'histoire récente des populations à l'aide de marqueurs nucléaires (AFLP) et des séquences de l'ADN mitochondrial (ADNmt), puis de mettre en relation ces résultats génétiques avec la diversité morphologique et la parasitologie des populations. Deux systèmes différents ont été étudiés : Au sein de l'aire native, l'étude se focalise sur le Limpopo inférieur et le sous-bassin de la Changane (Mozambique). Des patrons d'introgression incluant trois espèces en présence sont détectés, mais les hybrides sont peu fréquents et leur expansion limitée. Ces résultats sont de plutôt bonne augure pour la conservation d'O. mossambicus et ils permettent d'identifier deux zones de conservation prioritaires. L'étude des parasites indique une plus grande diversité parasitaire mais de faibles prévalences dans les sites de moindre valeur en conservation, ce qui pourrait favoriser le succès des espèces introduites et de leurs hybrides. Parmi les territoires envahis, les AFLP et l'ADNmt soutiennent une homogénéité générale et une diversité génétique faible, qui sont interprétées comme le résultat d'un fort goulot d'étranglement précédant l'expansion à l'échelle mondiale. Une structure des populations en lien avec la géographie à large échelle (Nouvelle-Calédonie, Guadeloupe, Jamaïque) est cependant détectée. La variation de la forme du corps est également structurée à large échelle géographique, ce en dépit des fortes variations environnementales enregistrées à l'échelle locale. Cela suggère un effet des contraintes génétiques sur la diversification morphologique contemporaine. L'absence de parasites monogènes sur les populations introduites en Nouvelle-Calédonie peut être mise en relation avec un évènement fondateur, et est proposé comme l'un des facteurs ayant pu favoriser le succès de l'espèce. En conclusion, une faible diversité génétique ne contraint vraisemblablement pas un potentiel envahissant élevé et une diversification rapide chez les tilapias.
Libros sobre el tema "Propagule pressure"
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National Research Council (U.S.). Water Science and Technology Board, ed. Assessing the relationship between propagule pressure and invasion risk in ballast water. Washington, D.C: National Academies Press, 2011.
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Committee on Assessing Numeric Limits for Living Organisms in Ballast Water, Water Science and Technology Board, Division on Earth and Life Studies y National Research Council. Assessing the Relationship Between Propagule Pressure and Invasion Risk in Ballast Water. National Academies Press, 2011.
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Assessing the Relationship Between Propagule Pressure and Invasion Risk in Ballast Water. Washington, D.C.: National Academies Press, 2011. http://dx.doi.org/10.17226/13184.
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Committee on Assessing Numeric Limits for Living Organisms in Ballast Water, Water Science and Technology Board, Division on Earth and Life Studies y National Research Council. Assessing the Relationship Between Propagule Pressure and Invasion Risk in Ballast Water. National Academies Press, 2011.
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Committee on Assessing Numeric Limits for Living Organisms in Ballast Water, Water Science and Technology Board, Division on Earth and Life Studies y National Research Council. Assessing the Relationship Between Propagule Pressure and Invasion Risk in Ballast Water. National Academies Press, 2011.
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Hale-Dorrell, Aaron T. Corn Crusade. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190644673.001.0001.
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Almost everyone has long misinterpreted Nikita Khrushchev’s ten-year crusade to propagate the cultivation of corn, a crop important across the globe but previously rare across the vast, environmentally diverse Soviet Union. Launched in 1953, this campaign comprised a large part of the new leadership’s efforts to remedy agrarian crises inherited from Iosif Stalin. Khrushchev pressured collective and state farms to increase plantings of corn from an insignificant proportion of their crops to a peak of nearly 20 percent. Expected to feed livestock that were to yield meat and dairy products, corn promised to enrich citizens’ meager, monotonous diets and thereby make good on Khrushchev’s infamous pledges that the Soviet Union was soon to “catch up to and surpass America” in the Cold War “peaceful competition” between communism and capitalism. Echoing Khrushchev’s former comrades, who denounced corn as “harebrained scheming” when ousting him in 1964, scholars have ridiculed it as “an irrational obsession.” Newly available archival documents reveal a more complex and interesting story of how Khrushchev borrowed industrial-farming methods from the United States. Following experts’ advice, he believed that hybrid seeds, machines, agronomy, and other technologies constituting the global trends in farming technology promised even greater increases in productivity under conditions found in the Soviet Union. Yet Khrushchev’s programs achieved only partial success because they could not overcome the entrenched interests, bureaucratic inertia, and competing priorities that encouraged government officials, local authorities, and farmworkers to disregard methods required to grow even modest harvests, let alone the bumper crops that Khrushchev envisioned.
Capítulos de libros sobre el tema "Propagule pressure"
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Johnston, Emma L., Richard F. Piola y Graeme F. Clark. "The Role of Propagule Pressure in Invasion Success". En Biological Invasions in Marine Ecosystems, 133–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-79236-9_7.
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Ricciardi, Anthony, Lisa A. Jones, Åsa M. Kestrup y Jessica M. Ward. "Expanding the Propagule Pressure Concept to Understand the Impact of Biological Invasions". En Fifty Years of Invasion Ecology, 225–35. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444329988.ch17.
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Meyerson, Laura A. y Petr Pyšek. "Manipulating Alien Plant Species Propagule Pressure as a Prevention Strategy for Protected Areas". En Plant Invasions in Protected Areas, 473–86. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-7750-7_21.
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Parker, John D., John L. Devaney y Nathan P. Lemoine. "Biotic resistance to plant invasions." En Plant invasions: the role of biotic interactions, 177–91. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0177.
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Abstract Biotic resistance to plant invasions takes many forms: consumption by native herbivores, competition with native plants and infection by native pathogens. But how often does biotic resistance prevent the damaging monocultures that typify the most problematic plant invaders, and how often is biotic resistance overwhelmed by the direct and indirect impacts of human activities? This chapter attempts to answer these questions, drawing on the long history of research into biotic resistance. We first briefly describe the major forms of biotic resistance to exotic plant invasions as an antecedent to other, more detailed chapters on competition, herbivory and pathogens. We then describe a new neutral model where variance in disturbance promotes invasions over the short term, but over longer timescales only propagule pressure drives invasions. These findings are a cautionary tale; pending increases in global trade and travel, particularly to the tropics, may provide the prerequisite disturbance and propagule pressure needed to ultimately stoke further invasions. Finally, we highlight case studies where invasions have been mitigated by restoration of biotic resistance from native herbivores and competitors. These studies provide strong empirical support that conservation of native biodiversity can be a nature-based solution to some invasions, although it remains to be seen if climate change will alter these effects over longer timescales.
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Traveset, Anna y David M. Richardson. "Plant invasions: the role of biotic interactions - an overview." En Plant invasions: the role of biotic interactions, 1–25. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0001.
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Abstract Diverse biotic interactions between non-native plant species and other species from all taxonomic groups are crucial mediators of the dynamics of plant invasions. This chapter reviews the key hypotheses in invasion ecology that invoke biotic interactions to explain aspects of plant invasion dynamics. We examine the historical context of these hypotheses and assess the evidence for accepting or rejecting their predictions. Most hypotheses invoke antagonistic interactions, mainly competition, predation, herbivory interactions and the role of pathogens. Only in the last two decades have positive (facilitative/mutualistic) interactions been explicitly included in invasion biology theory (as in ecological theory in general). Much information has accumulated in testing hypotheses relating to biotic resistance and Enemy Release Theory, although many of the emerging generalizations are still contentious. There is growing consensus that other drivers of plant invasion success, such as propagule pressure and disturbance, mediate the outcome of biotic interactions, thereby complicating our ability to make predictions, but these have rarely been assessed in both native and adventive ranges of non-native invasive species. It is also widely acknowledged that biogeographic comparisons, more than common garden experiments, are needed to shed light on many of the contradictory results. Contrasting findings have also emerged in exploring the roles of positive interactions. Despite strong evidence that such interactions are crucial in many communities, more work is needed to elucidate the factors that influence the relative importance of positive and negative interactions in different ecosystems. Different types of evidence in support of invasional meltdown have emerged for diverse habitats and across spatial scales. In light of increasing evidence that biotic indirect effects are crucial determinants of the structure, dynamics and evolution of ecological communities, both direct and indirect interactions involving native and non-native species must be considered to determine how they shape plant invasion patterns and the ecological impacts of non-native species on recipient communities. Research that examines both biotic interactions and the factors that mediate their strength and alter interaction outcomes is needed to improve our ability to predict the effects of novel interactions between native and non-native species, and to envisage how existing invaded communities will respond to changing environmental conditions. Many opportunities exist for manipulating biotic interactions as part of integrated control strategies to reduce the extent, density and impacts of non-native plant invasions. These include the introduction of species from the native range of the non-native plant for biological control, diverse manipulations of plant - herbivore interactions and many types of interaction to enhance biotic resistance and steer vegetation recovery following non-native plant control.
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"Propagule Pressure". En Encyclopedia of Biological Invasions, 561–63. University of California Press, 2019. http://dx.doi.org/10.1525/9780520948433-125.
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Parker, John D., John L. Devaney y Nathan P. Lemoine. "Biotic resistance to plant invasions." En Plant invasions: the role of biotic interactions, 177–91. CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0009.
Texto completoResumen
Biotic resistance to plant invasions takes many forms: consumption by native herbivores, competition with native plants and infection by native pathogens. But how often does biotic resistance prevent the damaging monocultures that typify the most problematic plant invaders, and how often is biotic resistance overwhelmed by the direct and indirect impacts of human activities? This chapter attempts to answer these questions, drawing on the long history of research into biotic resistance. We first briefly describe the major forms of biotic resistance to exotic plant invasions as an antecedent to other, more detailed chapters on competition, herbivory and pathogens. We then describe a new neutral model where variance in disturbance promotes invasions over the short term, but over longer timescales only propagule pressure drives invasions. These findings are a cautionary tale; pending increases in global trade and travel, particularly to the tropics, may provide the prerequisite disturbance and propagule pressure needed to ultimately stoke further invasions. Finally, we highlight case studies where invasions have been mitigated by restoration of biotic resistance from native herbivores and competitors. These studies provide strong empirical support that conservation of native biodiversity can be a nature-based solution to some invasions, although it remains to be seen if climate change will alter these effects over longer timescales.
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Hanley, Will. "Epilogue". En Identifying with Nationality, 280–96. Columbia University Press, 2017. http://dx.doi.org/10.7312/columbia/9780231177627.003.0014.
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For a dozen critical years, between 1914 (when Ottoman sovereignty over Egypt was extinguished) and 1926 (when Egypt’s first recognized nationality law was passed), the status of Egyptians under private international law was uncertain. This was a period during which passport controls proliferated, statelessness became an issue of international concern, and many kinds of foreignness (foreign and dual nationals, foreign capital, and the mutamassirun) were under pressure in Egypt itself. This chapter shows the means that Egyptians used to propagate nationalization programs during this period, and the support they gleaned from the gathering international consensus around nationality, which came to be considered (for the first time) a universal and natural human attribute.
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Maun, M. Anwar. "Seed dispersal". En The Biology of Coastal Sand Dunes. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780198570356.003.0008.
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Dispersal is a term used for the dissemination of detached reproductive structures from parent plants to a new site. Disseminules include spores, seeds, fruits, whole inflorescences, whole plants, fragments of the parent plant, bulbs and bulbils. Fruit attributes related to a particular dispersal agent or dispersal syndromes are complex and have resulted from millions of years of evolution. In practice, dispersal is mainly local, although some species of sea coasts are well adapted for long-distance dispersal. Knowledge of the modes of plant dispersal is vital to the study of coastal dune ecology because of the clear correlation between diversity and dispersal mechanisms. From the evolutionary point of view, dispersal improves fitness of species: the progeny is able to colonize a new site and extend the range of the species. The fitness here will be defined as getting to a coastal site by using any vector for dispersal, colonization of the new site (germination, establishment and reproduction) and dispersal of the propagules of the immigrant from the new site. Dispersal confers many benefits to the populations of plant species. It reduces competition for limited space and resources in the parental location and the more widely dispersed the propagules, the greater are the chances for the offspring to colonize elsewhere. Dispersal increases the chances of survival and evolution of more fit strains of a species by occupying more diverse habitats than the parents, and speciation may eventually occur in response to new selective pressures. For species adapted to live along sea coasts, dispersal by sea is primarily directed for dissemination to another site by the sea coast. During dispersal several physiological changes may occur in the disseminules that facilitate colonization of the species at the new habitat. For example, Barbour (1972) reported that immersion of upper fruits of Cakile maritima in seawater stimulated their subsequent germination under controlled conditions. Seed coat dormancy may also be broken by abrasion of seeds in sand while being rolled along the sand surface. Considering the large number of species along coasts and on islands, only a very few species may be successfully disseminated in seawater.
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Kesseli, Juha, Andre S. Ribeiro y Matti Nykter. "Measuring Information Propagation and Processing in Biological Systems". En Open Information Management, 190–226. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-246-6.ch009.
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In this chapter the authors study the propagation and processing of information in dynamical systems. Various information management systems can be represented as dynamical systems of interconnected information processing units. Here they focus mostly on genetic regulatory networks that are information processing systems that process and propagate information stored in genome. Boolean networks are used as a dynamical model of regulation, and different ways of parameterizing the dynamical behavior are studied. What are called critical networks are in particular under study, since they have been hypothesized as being the most effective under evolutionary pressure. Critical networks are also present in man-made systems, such as the Internet, and provide a candidate application area for findings on the theory of dynamical networks in this chapter. The authors present approaches of annealed approximation and find that avalanche size distribution data supports criticality of regulatory networks. Based on Shannon information, they then find that a mutual information measure quantifying the coordination of pairwise element activity is maximized at criticality. An approach of algorithmic complexity, the normalized compression distance (NCD), is shown to be applicable to both dynamical and topological features of regulatory networks. NCD can also be seen to enable further utilization of measurement data to estimate information propagation and processing in biological networks.
Actas de conferencias sobre el tema "Propagule pressure"
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Lang, Scott A. y Trey W. Walters. "Accurately Predicting Transient Fluid Forces in Piping Systems Part 1: Fundamentals". En ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84740.
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Abstract Changes in the operation of piping systems — like valve closures or pump starts — propagate pressure waves that travel at acoustic velocity throughout the fluid. These pressure waves have considerable effect on forces, potentially generating dynamic loads upwards of 10,000 lbf (50 kN) in common configurations. Some estimation methods used in industry for estimating transient forces neglect terms that may be important in some cases. Calculating forces due to these transients without simplification for transient liquid or gas flow is presented here in detail.
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Molyneux, John, Raju Ananth y Jay Gillis. "Decompression Pressure Wave Loads in a Boiling Water Reactor (BWR) Due to Recirculation Pipe Break". En ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77781.
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This paper presents a theoretical and numerical investigation of one of the postulated accidents for Boiling Water Reactors (BWRs), namely, a double-ended guillotine break of recirculation outlet line that leads to a sudden depressurization locally at the recirculation outlet nozzle. The depressurization wave front thus formed will propagate inside the reactor leading to transient loads on the internals. The paper discusses the solution to this wave propagation problem.
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Nishiguchi, Isoharu, Fumitoshi Sakata y Seiichi Hamada. "Theoretical and Experimental Investigation of Pipe Wall Thinning Detection Using Guided Waves". En ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61655.
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A method to investigate pipe wall thinning using guided waves has been developed for pipes in thermal power generation facilities. In this paper, the reflection coefficient and the transmission coefficient are derived for the torsional waves which propagate along a pipe and a simplified method to predict the waveform is proposed. The predictions of the waveforms by the FEM and a simplified method based on the reflection of torsional waves are also examined by comparing with experimental data.
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Broussard, John E. y Wayne Lunceford. "BWR Shroud Weld Off-Axis Crack Growth Investigation". En ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-66151.
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Recent inspections have identified cracking in the core shroud that is atypical in that the cracks exhibit characteristics inconsistent with traditionally reported intergranular stress corrosion cracking (IGSCC) occurring within stainless steel weld heat-affected zones (HAZs). These flaws are oriented transverse to the weld and are observed to propagate significantly beyond the weld HAZ. This paper describes the investigations which have been performed to quantify the likely limits on growth of these “off-axis” SCC cracks. The investigation includes welding residual stress analysis to determine the stress field present adjacent to the weld and crack tip SIF calculations for the bivariant stress field.
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Preece, Dale S. y W. Venner Saul. "Blastwall Effects on Down Range Explosively-Induced Overpressure". En ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1826.
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Blastwalls are often assumed to be the answer for facility protection from malevolent explosive assault, particularly from large vehicle bombs (LVB’s). The assumption is made that the blastwall, if it is built strong enough to survive, will provide substantial protection to facilities and people on the side opposite the LVB. This paper will demonstrate through computer simulations and experimental data the behavior of explosively induced air blasts during interaction with blastwalls. It will be shown that air blasts can effectively wrap around and over blastwalls. Significant pressure reduction can be expected on the downstream side of the blastwall but substantial pressure will continue to propagate. The effectiveness of the blastwall to reduce blast overpressure depends on the geometry of the blastwall and the location of the explosive relative to the blastwall.
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Luo, Jiacheng, Li Yu, Pengzhou Li y Lei Sun. "Structure Integrity Evaluation of Supercritical Water Cooled Pressure Tube Subjected to Accident Conditions". En ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-85017.
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The coolant inside the supercritical water cooled pressure tube operates beyond the critical thermodynamics point of water, and the structure integrity of the pressure tube is of great important to the safety of reactor. Under the accident load, the difference in temperature along the pressure tube wall will cause relatively large thermal stress. Due to the generated high tensile stress, coupled with the internal high pressure load, the defects in the inner surface of the pressure tube may propagate rapidly and even through the wall thickness. This paper investigates the structure integrity of the supercritical water cooled pressure tube based on the deterministic and the probabilistic method of fracture mechanics, and obtains the stress intensity factor and the probabilistic function. It is found that the integrity of the supercritical pressure tube can be maintained from the fracture mechanics analysis under the accident load.
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Larrosa, Nicolas O., Mirco D. Chapetti y Robert A. Ainsworth. "Assessing Fatigue Endurance Limit of Pitted Specimens by Means of an Integrated Fracture Mechanics Approach". En ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45562.
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From an operator/engineering perspective, the correct assessment of the severity of corrosion defects (e.g., pits) can have enormous economic, social and environmental benefits; therefore the development of a generally applicable and simple to apply procedure for fatigue assessment of key components is recognised as a valuable tool, seeking to reduce the current overly conservative procedures whilst maintaining structural integrity. The critical condition for a crack emanating from a pit (pit-to-crack transition) to start to propagate is analysed in this paper. The pitcrack configuration is re-characterized into that of a hemispherical crack of length equal to the pit depth, and this assumption is analysed by detailed 3D FEA. A propagation threshold approach is used to estimate the fatigue resistance from intrinsic material properties. The proposed approach is validated by comparison with experimental results available in the open literature.
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Staats, Jeremy C. y David A. Osage. "Determination of Fracture Arrest Stress". En ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77998.
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Pressure vessel components constructed to the ASME B&PV Code, Section VIII, Divisions 1 and 2 that are not subject to Post Weld Heat Treatment (PWHT) have a fracture arrest stress value set equal to 10% of the Ultimate Tensile Strength (UTS) of the material. The fracture arrest stress designates an applied stress value for a material at or below which crack propagation would cease in a component with a small flaw. The fracture arrest stress value in the code is based upon work conducted by T. S. Robertson [1] and William S Pellini [2]. This work included testing of base metal and welded joints without significant constraint. Pellini concluded that for welded plates without constraint, localized residual stress fields, resulting from restraint of longitudinal shrinkage during cooling of the weld metal, act in a direction parallel to the weld and thus can only propagate cracks oriented in a direction normal to the localized residual stress (i.e. perpendicular to the weld joint). The perpendicular cracks may propagate into the base metal; however, these cracks will arrest due to lower or negligible residual stresses outside of the weld zone in the base metal. Therefore, for manufacture of components welded without significant constraint, i.e. manufacture of ships and atmospheric storage tanks, the fracture arrest stress value equal to 10% of the UTS appears to be valid. In the manufacture of pressure vessels, the geometrical constraint of typical weld joints results in a different residual stress distribution that have stress components that are orientated both parallel and perpendicular to the weld. Due to the presence of residual stresses perpendicular to the weld, small cracks parallel to the weld joint may result in unstable crack propagation or brittle fracture because they remain in the residual stress field. Therefore, the use of a fracture arrest stress value equal to 10% of the UTS detailed in paragraph 3.11.5.1 of the ASME Section VIII, Division 2, Part 3 criteria document may not be valid. A review of the work conducted by Robertson and Pellini and current code rules is provided and compared to fracture assessments results using procedures from API 579-1/ASME FFS-1 and ASME Section VIII, Division 2, Part 3.
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An, Bai, Takashi Iijima, Chris San Marchi y Brian Somerday. "Micromechanisms of Hydrogen-Assisted Cracking in Super Duplex Stainless Steel Investigated by Scanning Probe Microscopy". En ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28181.
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Understanding the micromechanisms of hydrogen-assisted fracture in multiphase metals is of great scientific and engineering importance. By using a combination of scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and magnetic force microscopy (MFM), the micromorphology of fracture surface and microcrack formation in hydrogen-precharged super duplex stainless steel 2507 are characterized from microscale to nanoscale. The results reveal that the fracture surfaces consist of quasi-brittle facets with riverlike patterns at the microscale, which exhibit rough irregular patterns or remarkable quasi-periodic corrugation patterns at the nanoscale that can be correlated with highly localized plastic deformation. The microcracks preferentially initiate and propagate in ferrite phase and are stopped or deflected by the boundaries of the austenite phase. The hydrogen-assisted cracking mechanisms in super duplex stainless steel are discussed according to the experimental results and hydrogen-enhanced localized plasticity theory.
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Gao, Zengliang, Weiming Sun, Weiya Jin, Ying Wang y Fang Zhang. "Fatigue Crack Growth Properties of 16MnR and 316L Steels at High Temperature". En ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71501.
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Fatigue failures often take place in high temperature pressure vessels and equipment because of fluctuation of pressure and temperature. Fatigue crack growth properties of materials at high temperatures are very important for safety assessment of high temperature equipment. A series of fatigue crack growth tests were carried out, and fatigue crack growth rates were determined at 25∼500°C for typical steels 316L and 16MnR. The laws of fatigue crack growth of two materials at different temperatures and the effect of temperature on fatigue crack growth rates were studied. The results show that the crack growth rates increase with temperature for 316L steel. Both the exponent n and constant C for Paris law change with temperature. The fatigue cracks of 16MnR propagate at 150 °C and 300 °C more slowly than at room temperature and 425 °C. The fatigue crack growth rate at 425 °C is the highest for temperature range of 25–425 °C.
Informes sobre el tema "Propagule pressure"
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Taylor, Laura. Propagule Pressure and Disturbance Drive the Spread of an Invasive Grass, Brachypodium sylvaticum. Portland State University Library, enero de 2000. http://dx.doi.org/10.15760/etd.41.
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