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The Freshwater Gastropods of Nebraska and South Dakota: A Review of Historical Records, Current Geographical Distribution and Conservation Status
I explore the historical and current distribution of freshwater snails in Nebraska and South Dakota. Current knowledge of the distribution of species of freshwater gastropods in the prairie states of South Dakota and Nebraska is sparse with no recent comprehensive studies. Historical surveys of gastropods in this region were conducted in the late 1800's to the early 1900's, and most current studies that include gastropods do not identify individuals to species. I summarize historical data from both states and provide recent survey results for this prairie region. Historical records suggest 31 species reside in Nebraska and 25 species reside in South Dakota. My survey includes 262 sites within eight EPA level III ecoregions and includes palustrine, riverine, reservoir, and lacustrine water bodies under a variety of hydrologic conditions. These recently sampled sites that contained snails had 1 to 6 species, with an average of 2.4 species per site, a total of 638 species records. I observed no snails at eight sample sites. I identified twenty total species in seven families within the two–state region. The five most abundant species were Physa gyrina, Helisoma trivolvis, Lymnaea elodes, Lymnaea caperata , and Gyraulus parvus were observed in all eight of the ecoregions sampled. Seven species were observed at five or fewer sites including two non-indigenous species, Bellamya chinensis and Melanoides tuberculata. Species similarity metrics demonstrate that many of the sampled ecoregions have similar species composition. Estimates from rarefaction analysis allow comparison of species richness among geographic covariates. The Prairie Coteau and the Middle Rockies regions of South Dakota are the most species rich areas within the region. Checkerboard analyses suggest that competition is responsible for species absences at some sample sites. Evaluation of the quartile incidence of species and comparison to historical data suggests three species are imperiled, one species is critically imperiled, and at least seven species, observed only in historic studies, may also be critically imperiled or extirpated. A strategy is needed to more fully explore and conserve freshwater gastropods in the region.
Ecology|Conservation biology|Natural Resource Management
Stephen, Bruce J, "The Freshwater Gastropods of Nebraska and South Dakota: A Review of Historical Records, Current Geographical Distribution and Conservation Status" (2018). ETD collection for University of Nebraska - Lincoln. AAI10976258.