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.

Microsporidian disease of the invasive amphipod Dikerogammarus villosus and the potential for its transfer to local invertebrate fauna

“…Agnew and Koella 1997;Vizoso and Ebert 2005;Slothouber-Galbreath et al 2004). A microsporidian disease has recently been discovered in European rivers associated to the invasive gammarid Dikerogammarus villosus (Crustacea, Amphipoda) (Wattier et al 2007;Ovcharenko et al 2010). Dikerogammarus villosus is one of the most invasive freshwater species, colonising major river systems of Western and Central Europe from its Ponto-Caspian origin Bollache et al 2004;Grabowski et al 2007a;Wattier et al 2007;Bacela et al 2008).…”

“…A microsporidian disease has recently been discovered in European rivers associated to the invasive gammarid Dikerogammarus villosus (Crustacea, Amphipoda) (Wattier et al 2007;Ovcharenko et al 2010). Dikerogammarus villosus is one of the most invasive freshwater species, colonising major river systems of Western and Central Europe from its Ponto-Caspian origin Bollache et al 2004;Grabowski et al 2007a;Wattier et al 2007;Bacela et al 2008). Due to several favourable life-history traits and to its top predator position in the food chain, D. villosus is able to outnumber rapidly other macroinvertebrate species in colonized areas (Dick and Platvoet 2000;Bollache et al 2004;Van Riel et al 2006;Pöckl 2007;Grabowski et al 2007b).…”

“…Due to several favourable life-history traits and to its top predator position in the food chain, D. villosus is able to outnumber rapidly other macroinvertebrate species in colonized areas (Dick and Platvoet 2000;Bollache et al 2004;Van Riel et al 2006;Pöckl 2007;Grabowski et al 2007b). Dikerogammarus villosus is the typical host for the microsporidia Cucumispora dikerogammari (Ovcharenko and Kurandina 1987;Wattier et al 2007, Ovcharenko et al 2010, which spreads out successfully with its host and was identified in many populations all over Europe (Wattier et al 2007). Its prevalence was variable between D. villosus populations, reaching peaks of about 72% prevalence in populations where the host has been established for 3-5 years (Wattier et al 2007).…”

“…Dikerogammarus villosus is the typical host for the microsporidia Cucumispora dikerogammari (Ovcharenko and Kurandina 1987;Wattier et al 2007, Ovcharenko et al 2010, which spreads out successfully with its host and was identified in many populations all over Europe (Wattier et al 2007). Its prevalence was variable between D. villosus populations, reaching peaks of about 72% prevalence in populations where the host has been established for 3-5 years (Wattier et al 2007). This microsporidium is transmitted between individual hosts mainly horizontally, but its presence in ovaries suggests it can occasionally be vertically transmitted (Wattier et al 2007;Ovcharenko et al 2010).…”

“…Its prevalence was variable between D. villosus populations, reaching peaks of about 72% prevalence in populations where the host has been established for 3-5 years (Wattier et al 2007). This microsporidium is transmitted between individual hosts mainly horizontally, but its presence in ovaries suggests it can occasionally be vertically transmitted (Wattier et al 2007;Ovcharenko et al 2010). Its massive presence in muscles suggests pathogenicity to its host, but no study was dedicated to specifically measure its virulence.…”