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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. [ABSTRACT FROM AUTHOR]

Recent studies have shown the oxygen isotopic composition (δ18O) of modern terrestrial gastropod shells is determined largely by the δ18O of precipitation. This implies that fossil shells could be used to reconstruct the δ18O of paleo-precipitation as long as the isotopic system, including the hydrologic pathways of the local watershed and the gastropod systematics, is well understood. In this study, we measured the δ18O values of 456 individual gastropod shells collected from paleowetland deposits in the San Pedro Valley, Arizona that range in age from ca. 29.1 to 9.8 ka. Isotopic differences of up to 2‰ were identified among the four taxa analyzed (Succineidae, Pupilla hebes, Gastrocopta tappaniana, and Vallonia gracilicosta), with Succineidae shells yielding the highest values and V. gracilicosta shells exhibiting the lowest values. We used these data to construct a composite isotopic record that incorporates these taxonomic offsets, and found shell δ18O values increased by ~4‰ between the last glacial maximum and early Holocene, which is similar to the magnitude, direction, and rate of isotopic change recorded by speleothems in the region. These results suggest the terrestrial gastropods analyzed here may be used as a proxy for past climate in a manner that is complementary to speleothems, but potentially with much greater spatial coverage. [ABSTRACT FROM AUTHOR]