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: 16.2). 10/2007; 22(9):454-64. DOI: 10.1016/j.tree.2007.07.002
Source: PubMed


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, Oct 12, 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; 24(16). DOI:10.1111/mec.13298 · 6.49 Impact Factor
    • "Multiple introductions involving different genetic lineages can play a significant role in counter-balancing the important loss of allelic richness and heterozygosity following introduction bottlenecks (Kolbe et al. 2004; Roman and Darling 2007; Dlugosch and Parker 2008). Secondary contact and gene flow ( " admixture " ) within the invaded range may occur through the release of selection against admixture in introduced populations (Verhoeven et al. 2011), with the potential consequence of promoting range expansion (Forsman et al. 2008). "
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    ABSTRACT: The successful introduction of the common genet (Genetta genetta) into Europe has been traditionally associated to the Muslim invasion of Iberia, although diverse evidence suggested an earlier arrival. In this study, we assessed genetic variation at 11 microsatellite loci in 199 individuals from the Mediterranean Basin and used approximate Bayesian computation (ABC) combining genotypes and published mitochondrial sequences. Our objectives were to (1) test alternative scenarios of introduction of the species in Europe, (2) re-assess the mitochondrial signatures of ‘introduction hotspots’ in Iberia, and (3) evaluate how post-introduction demographic processes have shaped genetic structure in the invaded range. ABC estimates favored a scenario of independent introductions from Maghreb into the Balearic Isl. and Iberia; the latter was dated between the Upper Palaeolithic and the end of Phoenicians’ influence. Patterns of genotypic diversity broadened the Andalusian introduction hotspot to the antique Tartessos Kingdom and suggested multiple introductions and/or long-term genetic drift. The best fit ABC scenario implied a natural spread from Iberia to France, but was in potential conflict with our delimitation of two genetic clusters (France and Iberia) in continental Europe. In fact, southwestern France populations showed a fair proportion of alleles shared with Maghreb and low levels of heterozygosity that may reflect subsequent introduction from Iberia, in line with the high error rates in favor of this alternative scenario. Significant patterns of isolation-by-distance among individuals within both genetic clusters are suggestive of natural dispersal from both Iberian and French introduction sites resulting in a secondary contact zone in northern Iberia. Overall, our study strongly suggests that the common genet was intentionally introduced in southern Iberia at a time antedating the Muslim invasion, possibly via Phoenicians’ commercial routes. Subsequent introduction in France, long-term genetic drift and admixture likely shaped the species genetic variation currently observed in continental Europe
    Biological Invasions 06/2015; 17(6):1-17. DOI:10.1007/s10530-015-0846-y · 2.59 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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