Dr. Rob Dillon, Coordinator

Tuesday, June 27, 2017

The Freshwater Gastropods of The Ohio: An Interim Report

By popular demand!  Several of you have requested copies of the presentation I contributed at the Society for Freshwater Science meeting in Raleigh earlier this month.  A pdf download is available for the clicking below.

My collaborators on the work were Ryan Evans of KYDOW, Mark Pyron of Ball State, Tom Watters of Ohio State, Will Reeves of the USDA in Ft. Collins, Richard Kugblenu of SUNY-Albany, and Jeff Bailey & Mike Whitman of WVDEP.  Here’s the abstract: 
We report preliminary results from a survey of the freshwater gastropod fauna from the Ohio River basin above Paducah, including western Pennsylvania and most of West Virginia, Ohio, Kentucky, and Indiana.  Our database of 4,746 records was almost entirely drawn from state natural resource agencies (36%), museums (30%) and our own original collections (30%), almost all personally examined and verified.  We report 66 species and subspecies of freshwater gastropods [1], the most common of which are Physa acuta (959 incidences), Ferrissia rivularis (536), and Pleurocera semicarinata (all subspecies combined 528).  Nine species were collected in but a single population, four of which seem to be legitimately rare, the remainder peripheral.  The distribution of commonness and rarity appeared log-2 bimodal, with mean 3.84 (14.3 incidences) and standard deviation 2.79 (6.9 incidences).  Our Ohio River basin results are compared to similar databases previously assembled from the Atlantic drainages and from East Tennessee, and the 99 species of the combined 13-state fauna ranked by their incidence.
 I should emphasize that the results as I offered them in Raleigh were very preliminary.  Subsequent to the submission of the abstract above, our GIS analysis suggested that a couple subregions of our study area had been oversampled, resulting in a prune of our database back from 4,746 records to 4,570.  And I have just returned from two weeks in the field, adding quite a few sample sites from northern Tennessee [2] and central Kentucky, as well as a very large and impressive slug of data from Illinois [3].

Several of you have also asked me when the finished FWGO site might be expected to appear online.  That date, to be precise, is Not Quite Yet.  But we’ll keep you posted… 


[1] We recognize 6 subspecies of freshwater gastropods in the FWGO study area: the pair Campeloma decisum crassulum and C. decisum (ss), the pair Pleurocera simplex ebenum and P. simplex (ss), the pair Pleurocera canaliculata acuta and P. canaliculata (ss), the pair Pleurocera laqueata alveare and P. laqueata (ss), and the trio Pleurocera semicarinata livescens, P. semicarinata obovata, and P. semicarinata (ss).  Thus the total species we analyzed on slide #7 of our June presentation was 60.

[2] Yes, the Green River drainage includes a sliver of north central Tennessee.  The faunal similarity between Kentucky and Tennessee has been one of the biggest surprises of the FWGO survey.

[3] A tip of the hat to our good friend Kevin Cummings for his gracious hosting at the Illinois Natural History Survey.


  1. Why stop at Paducah? Why not go down to the mouth at Cairo to complete the mainstem?

    1. Two answers. Answer #1 is that the FWGNA Project has been moving forward in state-sized chunks so far, publishing sites of 30-40 species every 3-4 years. And the Ohio drainage above Paducah is already much larger than that, and taken much longer. Answer #2 is that we're working on the Tennessee / Cumberland even as I write this reply. Give us a couple more years, OK?