Phylogeography of an endangered Western North American springsnail

Abstract

We provide the first genetic analysis of the Bruneau Hot Springsnail (Pyrgulopsis bruneauensis), a federally listed (endangered) hydrobiid gastropod that is distributed in spring-fed habitats along a short reach of the Bruneau River in southwestern Idaho and threatened with extinction by groundwater withdrawal. Partial sequences of mitochondrial cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit I (NDI) were obtained from 51 specimens from six sites spanning the narrow geographic range of P. bruneauensis. A Bayesian analysis of the combined dataset resolved this species as a well supported clade which differed from other regional congeners by 4.66–10.62% sequence divergence (COI). The 11 observed COI haplotypes in P. bruneauensis formed two divergent (1.42 ± 0.7%) subgroups that co-occurred at five of the six collecting sites. COI haplotype diversity was substantial (ranging up to 0.9111) in all but one sample, while nucleotide diversity was low (<0.01). AMOVA detected small but significant variation among sites, although only one sample was significantly differentiated by pairwise comparisons. Haplotype composition varied widely among the collecting localities and no obvious geographic pattern was detected. These findings suggest that translocation of snails, which was considered as a possible measure in the P. bruneauensis recovery plan, should be preceded by assays to ensure selection of appropriately genetically diverse source populations.