Reduction in post-invasion genetic diversity in Crangonyx pseudogracilis (Amphipoda: Crustacea): A genetic bottleneck or the work of hitchhiking vertically transmitted microparasites?

Biological Invasions (Impact Factor: 2.59). 01/2010; 12(1). DOI: 10.1007/s10530-009-9442-3
Source: OAI


Parasites can strongly influence the success of biological invasions. However, as invading hosts and parasites may be derived from a small subset of genotypes in the native range, it is important to examine the distribution and invasion of parasites in the context of host population genetics. We demonstrate that invasive European populations of the North American Crangonyx pseudogracilis have experienced a reduction in post-invasion genetic diversity. We predict that vertically transmitted parasites may evade the stochastic processes and selective pressures leading to enemy release. As microsporidia may be vertically or horizontally transmitted, we compared the diversity of these microparasites in the native and invasive ranges of the host. In contrast to the reduction in host genetic diversity, we find no evidence for enemy release from microsporidian parasites in the invasive populations. Indeed, a single, vertically transmitted, microsporidian sex ratio distorter dominates the microsporidian parasite assemblage in the invasive range and appears to have invaded with the host. We propose that overproduction of female offspring as a result of parasitic sex ratio distortion may facilitate host invasion success. We also propose that a selective sweep resulting from the increase in infected individuals during the establishment may have contributed to the reduction in genetic diversity in invasive Crangonyx pseudogracilis populations.

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    • "However, a recent study has found no evidence for genetic bottlenecks during the Ponto-Caspian invasion of the amphipod crustacean Dikerogammarus villosus or its associated microparasites (Wattier et al., 2007). An even more complicated parasite system is that of the amphipod, Crangonyx pseudogracilis, which exhibits a reduction in post-invasion genetic diversity while its associated microparasites do not (Slothouber-Galbreath et al. 2010). Our review therefore suggests that much remains to be understood regarding post-invasion freshwater parasite systems, and there is great potential for comparable global studies in native and introduced freshwater populations that would help resolve questions regarding host versus parasite genetic diversity patterns. "
    Analysis of Genetic Variation in Animals, 02/2012; , ISBN: 978-953-51-0093-5
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    • "However, evidence of ERH's role during Crustacea invasion is lacking (Roy et al. 2011). While increased growth rates of the green crab C. maenas were recorded in its invasive range in the absence of a castrating parasite (Torchin et al. 2001), other IAC, such as the amphipod Crangonyx pseudogracilis (Bousfield), show no sign of reduced parasite burden Invasive alien Crustacea 581 (Slothouber Galbreath et al. 2010). In contrast, recent evidence suggests that parasites facilitate invasions by increasing the predatory impact of some IAC (Dunn 2009). "
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