Dr. Rob Dillon, Coordinator

Tuesday, April 9, 2024

The Freshwater Gastropods of The Great Plains

We are pleased to announce a major expansion of the FWGNA Project, now extending our coverage westward to include the prairie states of Kansas, Nebraska, South Dakota, and North Dakota.  The Freshwater Gastropods of the Great Plains, by Bruce J. Stephen, Robert T. Dillon, Jr, and Martin Kohl is now online and available for reference!  Check it out:

Visit the FWGGP

In this important new web resource, we report the results of an original survey of 795 rivers, streams, lakes, and ponds across a big slice of the American heartland, documenting 33 gastropod species.  For each species we provide range maps and ecological notes, with a photo gallery and a dichotomous key for easy identification.

Although in areal extent our 308,000 square mile Great Plains study area is the largest of the eight regions thus far covered by the FWGNA Project, by freshwater gastropod species richness it is the smallest.  We suggest two historical factors to account for the relative poverty of the Great Plains malacofauna: the absence of landform diversity, and the absence of time sufficient for a regionally adapted fauna to evolve.  The effects of Pleistocene glaciation, if any, seem to have been to increase species richness.  State subtotals were 16 species in Kansas, 18 in Nebraska, 19 in South Dakota, and 23 in North Dakota.

We also document reductions in species richness for three of the four Great Plains states when compared to expectation from the published literature.  Kansas seems to have lost 4 species, South Dakota 6 and Nebraska 14.  The freshwater gastropod species apparently missing from each state typically become more common further north.  Although some of this phenomenon is certainly due to sampling error, we think it likely that climate change may have been a factor in the decreased species richness of The Great Plains.