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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    • "Electronic supplementary material The online version of this article (doi:10.1007/s10530-015-1005-1) contains supplementary material, which is available to authorized users. source populations is traditionally expected in invasive populations, because of founder effects and genetic bottlenecks (Wares et al. 2005; Roman and Darling 2007; Handley et al. 2011), as observed recently in the invasive Corbicula clams (Pigneur et al. 2014). However, high propagule pressure and multiple introductions, leading to high levels of genetic diversity in invasive populations, are common in successful aquatic invasions (reviewed in Cristescu 2015). "
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    ABSTRACT: Genetic tools have been extremely useful to study the colonization history and dynamics of invasive species and infer source populations. In addition, understanding the distribution of genetic diversity of non-indigenous species is important to understand factors contributing to invasive success. Here, we used genetic markers to study the invasion history of the quagga mussel Dreissena rostriformis (Deshayes 1838). The invasion of North American and European watercourses by the quagga mussel is of major concern since this dreissenid mussel has widespread ecological and economic impacts in invaded regions. Through the use of mitochondrial (COI) and nuclear (microsatellites) markers and based on a large sampling, including both native and invasive ranges, we characterized the recent invasion of Western Europe by D. rostriformis. Scenario testing Bayesian analysis (approximate Bayesian computation methods) suggests that Western Europe was most probably invaded from the Pontic region via the southern corridor (Danube River, the Main-Danube Canal and the Main and Rhine rivers). Furthermore, pairwise FST values suggest a second invasion to Western Europe from North America via trans-Atlantic shipping. The high genetic diversity and low differentiation among D. rostriformis populations suggest high propagule pressure and frequent exchanges between the Pontic region, Eastern North America and Western Europe. Our study concludes that multiple introductions and high propagule pressure have shaped the genetic composition of populations in Western Europe. The results provide valuable information for future management plans in order to control the spread of highly invasive aquatic species.
    Biological Invasions 10/2015; DOI:10.1007/s10530-015-1005-1 · 2.59 Impact Factor
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    • "There are some particular aspects of the histories of species that may explain why purging is more likely during invasion than for stable metapopulations of native species. False brome and many other invasive species have succeeded partly as a consequence of multiple introductions of genetically divergent individuals (Dlugosch and Parker 2008; Facon et al. 2008; Roman and Darling 2007; Rosenthal et al. 2008). Our simulations demonstrate that invasions initiated with higher levels of genetic divergence have more potential for elevating absolute fitness through the elimination of deleterious mutations contributing to genetic load. "
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    ABSTRACT: Invasive species often display high fitness despite bottlenecks and inbreeding during establishment. We address this paradox through simulations and experiments that assess the potential for purging of genetic load during range expansion. Success of invaders often depends on the production of vigorous inbred offspring allowing for rapid population growth after colonization. Substantial genetic load of out-breeding species reduces the fitness of offspring as inbreeding ensues during the establishment of populations. In our simulations, sustained selfing or outcrossing within isolated populations did little to remove deleterious mutations. Conversely, inbreeding combined with periodic gene flow resulted in efficient purging and accelerated rates of range expansion. Purging efficiency was dependent on initial genetic diversity levels, in line with predictions that multiple introductions facilitate invasion and the evolution of more aggressive invaders. Simulation predictions were tested using the invasive species Brachypodium sylvaticum. Homozygous populations on B. sylvaticum's range periphery displayed lower inbreeding depression compared to heterozygous populations near introduction sites. Empirical tests with B. sylvaticum demonstrate that purging of genetic load is a plausible scenario promoting range expansion during invasion.
    Biological Invasions 10/2015; DOI:10.1007/s10530-015-1001-5 · 2.59 Impact Factor
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    • "Although introduced invasive species suffer from genetic bottlenecks, they often overcome adverse effects of population reduction by genetic admixture via multiple introductions from the native range (Kolbe et al. 2004) and/or other successful introduced populations (invasive bridgehead effect, Lombaert et al. 2010; Benazzo et al. 2015). Given that multiple introductions and genetic admixture may enhance invasibility (Kolbe et al. 2004; Roman & Darling 2007; Marrs et al. 2008; Ward et al. 2008), the number of introductions may indicate risk of further regional spread of a species. Better understanding of the genetic diversity of introduced populations and vital source populations along with the number of introductions may be used to prevent further introductions and/or spread of invasive species by designing monitoring and quarantine strategies targeting the source area and the important vectors (Estoup & Guillemaud 2010). "
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    ABSTRACT: Sparse, incomplete and inappropriate historical records of invasive species often hamper invasive species management interventions. Population genetic analyses of invaders might provide a suitable context for the identification of their source populations and possible introduction routes. Here, we describe the population genetics of Heracleum persicum Desf. ex Fisch and trace its route of introduction into Europe. Microsatellite markers revealed a significantly higher genetic diversity of H. persicum in its native range, and the loss of diversity in the introduced range may be attributed to a recent genetic bottleneck. Bayesian cluster analysis on regional levels identified three and two genetic clusters in the native and the introduced ranges, respectively. A global structure analysis revealed two worldwide distinct genetic groups: one primarily in Iran and Denmark, the other primarily in Norway. There were also varying degrees of admixture in England, Sweden, Finland and Latvia. Approximate Bayesian computation indicated two independent introductions of H. persicum from Iran to Europe: the first one in Denmark and the second one in England. Finland was subsequently colonized by English populations. In contrast to the contemporary hypothesis of English origin of Norwegian populations, we found Finland to be a more likely source for Norwegian populations, a scenario supported by higher estimated historical migration from Finland to Norway. Genetic diversity per se is not a primary determinant of invasiveness in H. persicum. Our results indicate that, due to either pre-adaptations or rapid local adaptations, introduced populations may have acquired invasiveness after subsequent introductions, once a suitable environment was encountered. This article is protected by copyright. All rights reserved.
    Molecular Ecology 10/2015; DOI:10.1111/mec.13411 · 6.49 Impact Factor
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