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

Abstract

We studied the diversity of clonal lineages in US populations of the New Zealand mudsnail (Potamopyrgus antipodarum), focusing on the western states, using three different types of genetic markers: mtDNA, allozymes, and microsatellite DNA (msDNA) (Dybdahl and Drown in Biol Invasions 13:1663–1672, 2011). The comment by Hershler et al. (Biol Invasions, doi:10.1007/s10530-012-0184-2, 2012) raises issue with our msDNA data, claiming that we underestimated genotypic diversity. We chose to focus on msDNA alleles within the size range previously identified in several earlier studies of P. antipodarum, in order to increase the likelihood that we were scoring homologous amplification products. In contrast, Hershler et al. Biol Invasions 13:1663–1672, (2010) claimed that they identified alleles that are much larger, indicating greater genotypic diversity in one region (Snake River, ID). In our view, their results stand in contrast to previous work on msDNA diversity and mutational processes, which raises the issue that some of the very large fragments that they claimed were msDNA alleles may be been non-homologous amplification products. Nevertheless, the results of the two papers and analyses agree on the main conclusion of our paper: that only a few clonal lineages are present in the Snake River, Idaho, one of which is very common.