Comparative phylogeography of two Northern Rocky Mountain endemics: the widespread Anguispira kochi occidentalis and the narrow-range Anguispira nimapuna (Gastropoda: Discidae).

The Northern Rocky Mountain ecosystem supports rich biological diversity with many endemic and rare species. Extant endemics display two biogeographic patterns: widespread species with fragmented populations, and narrow-range endemics. These distributions are shown by the congeneric snails and . These two taxa are disjunct from the remaining species of the genus, which achieves its greatest diversity in eastern North America. Given the disjunct nature of and , we here present a mtDNA phylogeny of the genus that includes both eastern and western species to assess the phylogenetic position of and . We then reconstruct the demographic history of and by analysing current patterns of genetic variation and interpreting the results considering the historical biogeography of the region. Both and represent unique taxa that are genetically and geographically distinct from their congeners. The current distribution and genetic structure of has been shaped by both historical isolation in refugia and more recent northward shifts, whereas is represented by two populations with shallow divergence in an area of long-term habitat stability.