A conservation assessment of the freshwater gastropods of South Dakota based on historical records and recent observations

In South Dakota, like most U.S. states, up-to-date knowledge of the distribution of freshwater gastropod species is lacking and historical data suffers from a host of synonyms. I consulted literature records and online museum databases to compile a list of freshwater gastropods historically recorded for South Dakota. I used systematic studies and regional records to evaluate each historically-listed species reducing 54 nominal species to 25 expected to inhabit South Dakota. This, along with recent survey data from across the state, enable a benchmark conservation status to be established for the freshwater gastropods of South Dakota. My preliminary conservation evaluation indicates Planorbula armigera is critically imperiled (S1), while three species; Ferrissia rivularis, Campeloma decisum, and Amnicola limosus are imperiled (S2). The status of historical species not observed recently, and suspected inhabitants known from adjacent states are discussed.