Species delimitation of the Snail Darter, Percina tanasi, and its implications on U.S. conservation policy

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Thomas J. Near
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Due to specialized terminology and increasingly technical methods, current discourse on species delimitation is often restricted to phylogenetic scientists though its impact extends to conservation policy makers and environmental activists. In this study, we focus on the species delimitation of the Snail Darter (Percina Tanasi), a biological conservation icon that played a critical role in one of the first court cases to invoke the Endangered Species Act of 1973. Bayesian analysis of ddRAD-sequencing for 59 specimens of P. tanasi and 37 specimens of its sister species the Stargazing Darter (P. uranidea) revealed genetic diversity that is consistent with comparisons within, rather than between, species. Our results do not support the hypothesis that P. tanasi is a distinct lineage from P. uranidea. The protocols developed in this study may serve as a model for the assessing the distinctiveness of other at-risk species.