Microsatellite evidence of invasion and rapid spread of divergent New Zealand mudsnail (Potamopyrgus antipodarum) clones in the Snake River basin, Idaho, USA

Abstract

We used microsatellites to assess genetic diversity and spatial structuring of the invasive apomictic New Zealand mudsnail (Potamopyrgus antipodarum) in the initial focal area of its recent North American invasion, a portion of the upper Snake River basin (Idaho) that is segmented by a series of hydropower dams. Thirty-four samples (812 total snails) from a 368 km reach of this drainage were genotyped for six loci. Sixty-five distinct clones were detected and grouped into four divergent clusters based on chord distances. Genetic structuring of populations was generally low. Our results indicate that the founding population(s) of this invasion was composed of a small number of putative clonal lineages which spread rapidly within this fragmented watershed owing to the enhanced dispersal ability of these parthenogens. The substantial genetic variation documented in this study suggests that caution should be used in the application of biological control measures for this pest species.

The absence of genotypic diversity in a successful parthenogenetic invader

“…Given the shorter time in the western US populations since introduction for mutational input, it is not surprising that our survey revealed different microsatellite MLGs only in individuals that also differed in mtDNA or allozyme genotype. In contrast, a microsatellites survey of Snake River, ID, populations, Hershler et al (2010) scored more microsatellite alleles and MLGs. However, unlike our study, they used a range of allele sizes much larger than would be consistent with the current understanding of microsatellite variation in P. antipodarum (Weetman et al 2001(Weetman et al , 2002.…”

“…Our PCR protocols included a long extension reducing the presence of ''plus A'' peaks. Our microsatellite methods differ from those used in a recent survey of the Snake River in Idaho (Hershler et al 2010). Their scoring methods are less detailed, but their results show that they considered much wider allele size ranges (over 50 repeats) than expected from the known allelic variation in microsatellites in P. antipodarum (Weetman et al 2001(Weetman et al , 2002.…”

The exotic aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca): state of the art of a worldwide invasion

“…Mutation rate of this species has been found to be within the range of sexualreproduction species (Weetman et al 2006). Genetic diversity of P. antipodarum has been reported to be very low in North American and Australian populations where the invasion is relatively recent (Dybdahl and Drown 2011), although Hershler et al (2010) reported 65 distinct clones in the upper Snake river basin (ID, USA), resulting from clone division in new lineages through mutations. In the case of Europe, there are several clonal lineages as a consequence of the long invasion history (Ponder 1988;Weetman et al 2002).…”

Comments on “The absence of genotypic diversity in a successful parthenogenetic invader” by Mark Dybdahl and Devin Drown [Biological Invasions 13 (2011), 1663–1672]

“…If these alleles instead have a disjunct size distribution similar to that of the British populations, their size range could span more than 100 repeats. Hershler et al (2010) detected 12 alleles in the Pa56 locus in a survey of 34 US populations (n = 811). These ranged from 106 to 324 bp, differing by 109 repeats (Fig.…”

“…Inasmuch as the explicit purpose of their study was to provide a detailed description of genotypic diversity we see no reason for restricting the analysis of allelic variation in this a priori manner. Furthermore, given that there was no reason to assume that United States populations were founded by colonizers from Great Britain, it would have been more appropriate to focus on the (considerably larger) microsatellite allele size ranges that were previously documented in other United States populations (Hershler et al 2010) and within the native range of this species in New Zealand (Neiman and Lively 2004). Dybdahl and Drown (2011) ignored peaks that were outside of the range of allele sizes previously documented in British populations.…”