Diversification over deep and shallow temporal scales in the Holarctic genus Perpolita (Gastropoda: Gastrodontidae)

Abstract

The Holarctic land snail genus Perpolita was used to explore the influence of past and current biogeography on diversification. The number of empirically-supported species was determined using a consensus between mtDNA sequence, nDNA sequence, conchology, and geographic and ecological range with five valid temperate-boreal species (Perpolita binneyana, Perpolita electrina, Perpolita hammonis, Perpolita petronella, and Perpolita radiatella) being recognized. Only P. petronella was unchanged in both nomenclature and diagnostic characteristics with the remainder requiring alterations. Perhaps the most important of these was elevation of P. radiatella to a valid species, with its populations having been previously lumped either under European P. hammonis or North American P. electrina. Divergence times of 18.7–10.0 Mya were suggested through genome-wide SNPs in combination with the fossil record, indicating a pre-Pleistocene origin for all Perpolita species. Using genetically-confirmed diagnostic shell characters, we accumulated > 2000 valid occurrences and used these to estimate appropriate modern and Last Glacial Maximum climate extents for all species. These models suggest that modern intra-specific gene pool diversity may generally reflect Pleistocene palaeoclimatology.