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Christopher G Eckert - One of the best experts on this subject based on the ideXlab platform.
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plant reproductive systems and evolution during Biological Invasion
Molecular Ecology, 2008Co-Authors: Spencer C. H. Barrett, Robert I Colautti, Christopher G EckertAbstract:Recent Biological Invasions provide opportunities to investigate microevolution during contemporary timescales. The tempo and scope of local adaptation will be determined by the intensity of natural selection and the amounts and kinds of genetic variation within populations. In flowering plants, genetic diversity is strongly affected by interactions between reproductive systems and stochastic forces associated with immigration history and range expansion. Here, we explore the significance of reproductive system diversity for contemporary evolution during plant Invasion. We focus in particular on how reproductive modes influence the genetic consequences of long-distance colonization and determine the likelihood of adaptive responses during Invasion. In many clonal invaders, strong founder effects and restrictions on sexual reproduction limit opportunities for local adaptation. In contrast, adaptive changes to life-history traits should be a general expectation in both outbreeding and inbreeding species. We provide evidence that evolutionary modifications to reproductive systems promote the colonizing ability of invading populations and that reproductive timing is an important target of selection during range expansion. Knowledge of the likelihood and speed at which local adaptation evolves in invasive plants will be particularly important for management practices when evolutionary changes enhance ecological opportunities and invasive spread.
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interaction between founder effect and selection during Biological Invasion in an aquatic plant
Evolution, 2005Co-Authors: Agnes Kliber, Christopher G EckertAbstract:Long-distance colonization and rapid range expansion associated with Biological Invasion may have major evolutionary consequences via both stochastic processes and selection. Using large-scale population genetic surveys, we demonstrate a major shift in the relative frequency of sexually fertile diploid versus sexually sterile triploid populations associated with the Invasion of North America by a clonal aquatic plant, Butomus umbellatus. Most populations across the native European range were triploid (84% of 108), whereas most introduced populations were diploid (71% of 136). We evaluated the roles of stochastic processes versus natural selection in causing this shift by surveying predominantly neutral genetic variation at 28 RAPD loci. In Europe (EU) we detected 47 distinct genotypes among 142 plants sampled from 71 populations, whereas in North America (NA) we detected only six genotypes among 138 plants from 69 populations. Of the six NA genotypes, a set of four closely related genotypes were found only in triploid populations and a pair of closely related genotypes were found only in diploid populations, and these were genetically divergent from the triploid genotypes. This result is consistent with severe founder effect. Because sex creates genotypic variation and produces offspring with greater dispersal potential than those produced clonally, we tested the hypothesis that sexual reproduction characteristic of diploids has given them a colonization advantage that accounts for their high frequency in NA. However, we found little or no evidence of sexual recruitment in introduced diploids. One very widespread heterozygous genotype occurred in 95% of 38 introduced diploid populations (i.e., 72 of 76 plants surveyed) suggesting predominant clonal reproduction. Moreover genotypic diversity was not higher within or among diploid than triploid populations in either the native or introduced range. Low genetic diversity in diploid populations was also supported by a comparison of within-population quantitative variation for plant size under a common greenhouse environment. Thus, diploids have not been favored during colonization owing to their sexual fertility. However, concurrent studies have shown that NA diploids exhibit a much higher capacity for clonal reproduction, via small vegetative bulbils, than NA triploids, which almost never produce bulbils. The same difference in clonal capacity is not a consistent feature of the native EU populations. Taken together, these results suggest that strong founder effect has set the stage for a major increase in diploid frequency due to the particular, and possibly idiosyncratic, features of the diploid and triploid lineages introduced to North America.
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evolutionary increase in sexual and clonal reproductive capacity during Biological Invasion in an aquatic plant butomus umbellatus butomaceae
American Journal of Botany, 2005Co-Authors: Jeremy S Brown, Christopher G EckertAbstract:To test the hypothesis that increased allocation to reproduction is selected during Biological Invasion, we compared germination, survival, growth, and reproduction of native vs. introduced populations of the invasive aquatic plant Butomus umbellatus in a common greenhouse environment. Although seedling emergence and establishment did not differ consistently, survival thereafter was twice as high for eight introduced North American than eight native European populations. As predicted, introduced plants were more likely to produce sexual inflorescences and clonal asexual vegetative bulbils, and they invested much more biomass in both reproductive modes. Higher reproductive investment was due to higher proportional allocation of biomass rather than larger plant size. These results are consistent with selection for increased reproduction during range expansion. However, population genetic surveys indicate that recruitment from seed rarely occurs in introduced populations. Hence increased sexual allocation is not an adaptive response to Invasion. Although increased clonal reproduction may be advantageous in expanding populations, genetic evidence from introduced populations of B. umbellatus suggests that increased clonal allocation may have arisen via stochastic processes during long-distance transport or a selective filter right at introduction, rather than incremental natural selection during range expansion.
James J. Opaluch - One of the best experts on this subject based on the ideXlab platform.
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Analyze the risks of Biological Invasion
Stochastic Environmental Research and Risk Assessment, 2011Co-Authors: Meifeng Luo, James J. OpaluchAbstract:Introducing non-native species can create serious environmental risks, such as changing the attributes of ecosystem, displacing the native species, clogging the natural waterways and channels. Careful examination of the possible consequences before implementation can prevent the adverse consequences of invasive species. However, policy analysis for such an action is often difficult, due to the complexity of the marine environment, and the interactions among the species therein. This paper presents a spatial-explicit agent-based simulation model for analyzing the environmental risks of introducing non-native species, Suminoe oyster (Crassostrea ariakensis). It is considered to be introduced into the Chesapeake Bay, USA, where there is a native Oyster species (Eastern oyster, Crassostrea virginica) with declining population. The simulation result indicates that the non-native species will likely displace the native species, but this can be controlled by setting up a different harvest plan, and the location and the number of initial spat introduced.
Daniel Simberloff - One of the best experts on this subject based on the ideXlab platform.
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in search of a real definition of the Biological Invasion phenomenon itself
Biological Invasions, 2008Co-Authors: Loic Valery, Herve Fritz, Jeanclaude Lefeuvre, Daniel SimberloffAbstract:The many qualifying terms attributed to invasive species reveal the lack of precision surrounding the notion of Biological Invasion itself. In spite of several proposed definitions, some basic disagreements persist concerning characterization of the phenomenon. These primarily arise from the lack of pertinence of both of the main current criteria—the geographic (or biogeographic) criterion and the impact criterion—to what is really intended by “Invasion.” Faced with this situation, it seems preferable to adopt an ontological approach allowing a return to the basic principles of the elaboration of a definition. Starting with the nature of the phenomenon itself (i.e., its essence), we try to elucidate the notion of Biological Invasion and we suggest a general definition compatible with most of the ideas already expressed.
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ECOLOGICAL RESISTANCE TO Biological Invasion OVERWHELMED BY PROPAGULE PRESSURE
Ecology, 2005Co-Authors: Betsy Von Holle, Daniel SimberloffAbstract:Models and observational studies have sought patterns of predictability for Invasion of natural areas by nonindigenous species, but with limited success. In a field experiment using forest understory plants, we jointly manipulated three hypothesized determinants of Biological Invasion outcome: resident diversity, physical disturbance and abiotic conditions, and propagule pressure. The foremost constraints on net habitat invasibility were the number of propagules that arrived at a site and naturally varying resident plant density. The physical environment (flooding regime) and the number of established resident species had negligible impact on habitat invasibility as compared to propagule pressure, despite manipulations that forced a significant reduction in resident richness, and a gradient in flooding from no flooding to annual flooding. This is the first experimental study to demonstrate the primacy of propagule pressure as a determinant of habitat invasibility in comparison with other candidate controlling factors.
Santanu Roy - One of the best experts on this subject based on the ideXlab platform.
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controlling a Biological Invasion a non classical dynamic economic model
Economic Theory, 2008Co-Authors: Lars J Olson, Santanu RoyAbstract:This paper analyzes the optimal intertemporal control of a Biological Invasion. The Invasion growth function is non-convex and control costs depend on the Invasion size, resulting in a non-classical dynamic optimization problem. We cha- racterize the long run dynamic behavior of an optimally controlled Invasion and the corresponding implications for public policy. Both control and the next-period inva- sion size may be non-monotone functions of the current Invasion size; the related optimal time paths may not be monotone or convergent. We provide conditions under which eradication, maintenance control, and no control are optimal policies.
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on prevention and control of an uncertain Biological Invasion
Applied Economic Perspectives and Policy, 2005Co-Authors: Lars J Olson, Santanu RoyAbstract:This paper examines how optimal prevention and control policies depend on the economic and Biological characteristics of a randomly introduced Biological Invasion where the objective is to minimize the expected social costs from prevention, control, and Invasion damages. The results characterize how optimal prevention and control policies vary with the initial Invasion size, the Invasion growth rate, and the probability distribution of introductions. The paper also examines the conditions under which the optimal policy relies solely on either prevention or control, the conditions under which it is optimal to completely prevent new introductions, and the conditions under which eradication of established Invasions is optimal. (This abstract was borrowed from another version of this item.) (This abstract was borrowed from another version of this item.)
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on prevention and control of an uncertain Biological Invasion
2005Co-Authors: Lars J Olson, Santanu RoyAbstract:This paper examines how optimal prevention and control policies depend on the economic and Biological characteristics of a randomly introduced Biological Invasion where the objective is to minimize the expected social costs from prevention, control, and Invasion damages. The results characterize how optimal prevention and control policies vary with the initial Invasion size, the Invasion growth rate, and the probability distribution of introductions. The paper also examines the conditions under which the optimal policy relies solely on either prevention or control, the conditions under which it is optimal to completely prevent new introductions, and the conditions under which eradication of established Invasions is optimal.
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the economics of controlling a stochastic Biological Invasion
American Journal of Agricultural Economics, 2002Co-Authors: Lars J Olson, Santanu RoyAbstract:The Invasion of ecological systems by nonindigenous species is now recognized as a growing global problem that imposes significant economic and ecological damages. In the United States alone, the total costs of nonindigenous species have been estimated to be at least $137 billion per year (Pimentel et al.). Approximately one-fourth of the value of the country’s agricultural output is lost to nonindigenous plant pests or to the costs of controlling them (Simberloff). The economic damages from a single invasive species can be enormous. The costs of controlling the zebra mussel (Dreissena polymorpha) in the Great Lakes were estimated to reach $5 billion in 2001 (U.S. Geological Survey (USGS)) while the Russian wheat aphid (Diuraphis noxia) caused an estimated $600 million (1991$) in crop damages between 1987 and 1989 (Office of Technology Assessment (OTA)). Invasive species also cause significant ecological harm. They can alter ecosystem processes, act as vectors of disease, and reduce biodiversity (Vitousek et al.). Worldwide, out of 256 vertebrate extinctions with an identifiable cause, 109 are known to be due to Biological invaders. In comparison, seventy such extinctions are known to be caused by human exploitation (Cox). The potential for a single invasive species to cause irreparable ecological damage is manifest in the extinction of twelve of Guam’s native bird species following the Invasion of the island by the brown tree snake, Boiga irregularis, in the mid-twentieth century (Savidge).
Michael R Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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global indicators of Biological Invasion species numbers biodiversity impact and policy responses
Diversity and Distributions, 2010Co-Authors: Melodie A Mcgeoch, Stuart H M Butchart, Dian Spear, Elrike Marais, Elizabeth J Kleynhans, Andy Symes, Janice Chanson, Michael R HoffmannAbstract:Aim Invasive alien species (IAS) pose a significant threat to biodiversity. The Convention on Biological Diversity’s 2010 Biodiversity Target, and the associated indicator for IAS, has stimulated globally coordinated efforts to quantify patterns in the extent of Biological Invasion, its impact on biodiversity and policy responses. Here, we report on the outcome of indicators of alien Invasion at a global scale. Location Global. Methods We developed four indicators in a pressure-state-response framework, i.e. number of documented IAS (pressure), trends in the impact of IAS on biodiversity (state) and trends in international agreements and national policy adoption relevant to reducing IAS threats to biodiversity (response). These measures were considered best suited to providing globally representative, standardized and sustainable indicators by 2010. Results We show that the number of documented IAS is a significant underestimate, because its value is negatively affected by country development status and positively by research effort and information availability. The Red List Index demonstrates that IAS pressure is driving declines in species diversity, with the overall impact apparently increasing. The policy response trend has nonetheless been positive for the last several decades, although only half of countries that are signatory to the Convention on Biological Diversity (CBD) have IAS-relevant national legislation. Although IAS pressure has apparently driven the policy response, this has clearly not been sufficient and/or adequately implemented to reduce biodiversity impact. Main conclusions For this indicator of threat to biodiversity, the 2010 Biodiversity Target has thus not been achieved. The results nonetheless provide clear direction for bridging the current divide between information available on IAS and that needed for policy and management for the prevention and control of IAS. It further highlights the need for measures to ensure that policy is effectively implemented, such that it translates into reduced IAS pressure and impact on biodiversity beyond 2010.