Freshwater snails of the family Pleuroceridae are of high conservation priority, but little is known about their biology. The objective of this project is to infer the evolutionary relationships of Leptoxis (11 extant and 13 extinct species) and the recently extinct Gyrotoma (6 extinct species) in order to aid in defining biologically-relevant conservation units. Mitochondrial and nuclear DNA sequences of extant and recently extinct Leptoxis and Gyrotoma will be used to infer their evolutionary relationships. Dried tissue from shells that were deposited in natural history collections will be used to obtain DNA of extinct species. Inclusion of extinct species, in addition to extant species, will increase the robustness of evolutionary hypotheses resulting from this study. This will be the first evolutionary study that includes all Leptoxis and Gyrotoma species. Aquatic ecosystems are essential to the health of society, but these systems are subject to high levels of anthropogenic stress. The health of water resources in the southeastern U.S. depends on the continued survival of pleurocerid snails which are cornerstone species in these systems. The genus Leptoxis presents special conservation concerns as 13 Leptoxis species have gone extinct in the last 50 years. This project will ultimately increase the effectiveness of conservation plans for Leptoxis by aiding in the definition of management units.

Project Report

The primary goal of the funded project was to determine the phylogenetic position of recently extinct pleurocerid snails in relation to extant species. By including recently extinct species in phylogenetic hypotheses, we also aimed to help resolve relationships among species by increasing the overall taxon sampling for phylogenetic inference. Many of the extinct pleurocerids we included in our analyses were historically found in the Coosa River in Alabama, but we also included species from the Ohio River and Big Black River in Mississippi. DNA was extracted from dried tissue left in shells that were deposited at the North Carolina Museum of Natural Sciences in Raleigh, NC and the National Museum of Natural History in Washington DC. We sequenced three genes and performed phylogenetic inferences using standard methods. Our results determined that extinction in the family Pleuroceridae is spread across the family’s phylogeny. Although extinction is never positive, this scenario is considerably better than if multiple, distinct lineages had gone extinct. We also found evidence that many of the species that went extinct in the Coosa River may have simply been different shell forms of a single species, the Painted Rocksnail, rather than multiple species. This is another welcome finding considering fewer species than previously thought may have gone extinct. Overall, we found that the amount of genetic diversity that was lost from anthropogenically caused pleurocerid extinctions is likely not as high as previously hypothesized. Nevertheless, there is still a considerable need to conserve pleurocerid snails because many species have undergone drastic range reductions, and continued stress on freshwater resources will likely only further imperil the remaining species. This project also included undergraduate and graduate student training. In particular, four undergraduate students were trained in molecular biology techniques and had the opportunity to participate in NSF funded research as undergraduate students. This experience has shaped their career goals and allowed them to pursue graduate school and/or medical school in most cases. Our findings have also been incorporated in the outreach and educational efforts of the Alabama Aquatic Biodiversity Center in Marion, Alabama. The Alabama Aquatic Biodiversity Center is the largest non-game freshwater recovery center in the southeastern US, and it is maintained by the Alabama Department of Conservation and Natural Resources.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Simon Malcomber
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University of Alabama Tuscaloosa
United States
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