No genetic bottleneck or associated microparasite loss in invasive populations of a freshwater amphipod

Abstract

Understanding what factors determine the success of an invasive species in its adopted range is crucial from an evolutionary ecology point of view, because it can provide insights into which biological characteristics are required for survival in varied environmental conditions. Successful establishment may depend on both maintaining genetic diversity, which will allow the species to evolve and/or adapt to new environments, and the presence or absence of natural enemies such as parasites. We tested these two hypotheses by studying populations of the amphipod crustacean Dikerogammarus villosus . This Ponto-Caspian invader has rapidly and successfully invaded western Europe and threatens macroinvertebrate biodiversity in its adopted ranges. It is a unique system to study since both its colonisation history and its geographic origins are well-known. Using samples from the whole geographic range of the invasion route, and using four molecular markers, we found no evidence for genetic bottlenecks during the invasion of D. villosus in western Europe, despite slight variations in allelic proportions according to spatio-temporal subdivisions of our dataset. In addition, we analysed the prevalence and diversity of parasites across its native and adopted range. We found no macro-parasites, and no significant parasite loss of microsporidian parasites during the invasive process. Our data suggest that D. villosus invasion was either massive, or recurrent, or both, allowing a parasitic cortege to follow the host. The maintenance of genetic diversity may have contributed to its success, including the variation in resistance in the face of the natural enemies.

Success of the invasive Ponto-Caspian amphipod Dikerogammarus villosus by life history traits and reproductive capacity

“…The average specific growth rate G s which is expressed as a percentage of the rate of growth was estimated on the average to be 1.3 ± 0.5% length day -1 for males and 1.5 ± 0.4% length day -1 for females. The identical growth pattern for D. villosus populations in the Rivers Danube and Moselle is not surprising because according to Wattier et al (2007) D. villosus populations neither show loss of genetic diversity nor loss of parasites along their well documented colonisation corridor into Western Europe. Additionally, the amplitude in water temperature in the Rivers Danube and Moselle is almost identical.…”

Enemy release and genetic founder effects in invasive killer shrimp populations of Great Britain

“…No losses of genetic diversity or parasites were noted during the invasion of the Rhine, Rhone, Seine and Loire basins of mainland Europe by D. villosus (Wattier et al 2007). This is presumably due to high propagule pressure as D. villosus invaded in successive waves, involving high numbers of individuals, along the courses of rivers and canals.…”

“…The generalist predatory behaviour of D. villosus also impacts other aquatic invertebrates and places this invertebrate in competition with predatory fish (MacNeil et al 2010). Unusually, the colonisation history of this Ponto-Caspian species in Europe is well-documented (Wattier et al 2007). D. villosus is now wellestablished in major European river basins including the Danube, Vistula, Elbe, Oder, Rhine, Rhone, Seine and Loire, and has recently colonised Great Britain, occurring at four separate sites in southern England and Wales (Bojko et al 2013;MacNeil et al 2010).…”

“…This is presumably due to high propagule pressure as D. villosus invaded in successive waves, involving high numbers of individuals, along the courses of rivers and canals. However, some evidence supports the acquisition of new parasites during the expansion of D. villosus, since the microsporidia Nosema granulosis, Dictyocoela muelleri and Dictyocoela berillonum were not discovered in D. villosus within its native range but did occur within certain invasive populations in Europe (Wattier et al 2007). These, and other microsporidia also infect native British amphipods (Table 1), presenting a risk of transfer to invading D. villosus, even if it escapes its former parasitic enemies during transport to Great Britain.…”

Predicting the predatory impacts of the “demon shrimp” Dikerogammarus haemobaphes, on native and previously introduced species

“…Bacela-Spychalska et al 2014), populations (e.g. Müller et al 2002;Wattier et al 2007), and communities (e.g. Dick and Platvoet 2000;Dick et al 2002;van Riel et al 2006a, b).…”