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Roman, J. and J. A. Darling. Paradox lost: genetic diversity and the success of aquatic invasions. Trends Ecol. Evol.

Gund Institute for Ecological Economics, University of Vermont, 617 Main Street, Burlington, VT 05443, USA.
Trends in Ecology & Evolution (Impact Factor: 15.35). 10/2007; 22(9):454-64. DOI: 10.1016/j.tree.2007.07.002
Source: PubMed

ABSTRACT There is mounting evidence that reduced genetic diversity in invasive populations is not as commonplace as expected. Recent studies indicate that high propagule vectors, such as ballast water and shellfish transplantations, and multiple introductions contribute to the elimination of founder effects in the majority of successful aquatic invasions. Multiple introductions, in particular, can promote range expansion of introduced populations through both genetic and demographic mechanisms. Closely related to vectors and corridors of introduction, propagule pressure can play an important role in determining the genetic outcome of introduction events. Even low-diversity introductions have numerous means of avoiding the negative impact of diversity loss. The interaction of high propagule vectors and multiple introductions reveal important patterns associated with invasion success and deserve closer scrutiny.

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Available from: John A Darling, Aug 30, 2015
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    • "The founding population comprised few genotypes, possibly only one clone, resulting in inbreeding. Subsequent introductions from the same or very similar source populations contributed to an increase of genetic variation which may have facilitated the successful establishment of the population (Sakai et al. 2001; Kolbe et al. 2004; Frankham 2005b; Roman & Darling 2007; Dlugosch & Parker 2008; Forsman 2014; Rius & Darling 2014; Bock et al. 2015). Interestingly, 'European D. pulicaria' with the same mitochondrial haplotype as found in LLC has been detected for the first time in the pelagial of the nearby Lake Greifensee in winter 2012. "
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    ABSTRACT: Biological invasions are a global issue with far-reaching consequences for single species, communities and whole ecosystems. Our understanding of modes and mechanisms of biological invasions requires knowledge of the genetic processes associated with successful invasions. In many instances, this information is particularly difficult to obtain as the initial phases of the invasion process often pass unnoticed and we rely on inferences from contemporary population genetic data. Here, we combined historic information with the genetic analysis of resting eggs to reconstruct the invasion of Daphnia pulicaria into Lower Lake Constance (LLC) in the 1970s from the resting egg bank in the sediments. We identified the invader as 'European D. pulicaria' originating from meso- and eutrophic lowland lakes and ponds in Central Europe. The founding population was characterised by extremely low genetic variation in the resting egg bank that increased considerably over time. Furthermore, strong evidence for selfing and/or biparental inbreeding was found during the initial phase of the invasion, followed by a drop of selfing rate to low levels in subsequent decades. Moreover, the increase in genetic variation was most pronounced during early stages of the invasion, suggesting additional introductions during this period. Our study highlights that genetic data covering the entire invasion process from its beginning can be crucial to accurately reconstruct the invasion history of a species. We show that propagule banks can preserve such information enabling the study of population genetic dynamics and sources of genetic variation in successful invasive populations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Molecular Ecology 06/2015; DOI:10.1111/mec.13298 · 6.49 Impact Factor
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    • "Moreover, admixture following multiple introductions from divergent source regions represents a fundamental restructuring of genetic variation from differentiation among populations into standing genetic variation within populations. A rich body of research examining inter-and intraspecific hybridization suggests at least three scenarios in which genetic restructuring could affect the evolution of invasive species (see Lee 2002; Seehausen 2004; Roman & Darling 2007; Rius & Darling 2014). These are briefly outlined below (see also Bock et al. "
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    ABSTRACT: Biological invasions are 'natural' experiments that can improve our understanding of contemporary evolution. We evaluate evidence for population differentiation, natural selection and adaptive evolution of invading plants and animals at two nested spatial scales: (i) among introduced populations (ii) between native and introduced genotypes. Evolution during invasion is frequently inferred, but rarely confirmed as adaptive. In common garden studies, quantitative trait differentiation is only marginally lower (~3.5%) among introduced relative to native populations, despite genetic bottlenecks and shorter timescales (i.e. millennia vs. decades). However, differentiation between genotypes from the native vs. introduced range is less clear and confounded by nonrandom geographic sampling; simulations suggest this causes a high false-positive discovery rate (>50%) in geographically structured populations. Selection differentials (¦s¦) are stronger in introduced than in native species, although selection gradients (¦β¦) are not, consistent with introduced species experiencing weaker genetic constraints. This could facilitate rapid adaptation, but evidence is limited. For example, rapid phenotypic evolution often manifests as geographical clines, but simulations demonstrate that nonadaptive trait clines can evolve frequently during colonization (~two-thirds of simulations). Additionally, QST -FST studies may often misrepresent the strength and form of natural selection acting during invasion. Instead, classic approaches in evolutionary ecology (e.g. selection analysis, reciprocal transplant, artificial selection) are necessary to determine the frequency of adaptive evolution during invasion and its influence on establishment, spread and impact of invasive species. These studies are rare but crucial for managing biological invasions in the context of global change. © 2015 John Wiley & Sons Ltd.
    Molecular Ecology 04/2015; Online Early(9). DOI:10.1111/mec.13162 · 6.49 Impact Factor
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    • "The more plausible explanations for our findings seem to be related with propagule pressures and multiple introductions as describe by Roman and Darling (2007). Different diversity of the sources, sizes of the inoculums, numbers of introduction events and finally different extent of bottleneck processes in the new environments can determine different results for the same species in different scenarios (Frankham 2005; Roman & Darling 2007; Dlugosch & Parker 2008). On the other hand, a process of purifying selection at the beginning of the invasion followed by a population expansion cannot be discarded for Villaviciosa. "
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    ABSTRACT: Estuaries are among the most important habitats of coastal areas. However, they are significantly affected by human activities worldwide, threatening their resources and the commercial uses depending on them. Fisheries and aquaculture are some of the main factors affecting the estuarine ecosystems today. In this work, we pursue the aims of genetically identifying the cultured and harvested oyster and razor clam species inhabiting Asturian estuaries (Eo, Ribadesella and Villaviciosa) and describing the genetic diversity and patterns of genetic connectivity between those species in these estuaries. The results revealed the almost complete dominance of the introduced Crassostrea gigas as the species that supports the oyster’s production in Asturias with a striking diversity of gene pools in wild environments (R�ıa de Villaviciosa and Ribadesella) which significantly exceeds the diversity found in the hatcheries seeds commonly used for culturing. Moreover, we detected two different species of Ensis sp. inhabiting the Asturian estuaries: Ensis ensis inside R�ıa del Eo and Ensis directus, an invasive species, in R�ıa de Villaviciosa. Significant genetic differentiation between estuaries for the exotic oyster C. gigas and also for the native razor clam Solen marginatus were found. These results suggest Asturian estuaries are not a single management unit for some species and thus prevention must be taken for avoiding intentional or human-mediated translocations among them. Biodiversity monitoring for discovering newcomer invasive species, measures for environmental recovery of these ecosystems and strict controls to avoid increasing of harvesting pressures are also a necessity to improve the management of these relevant ecosystems.
    Aquaculture Research 03/2015; DOI:10.1111/are.12745 · 1.32 Impact Factor
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