Conservation genetics of two endangered unionid bivalve species, Epioblasma florentina walkeri and E-Capsaeformis (Unionidae: Lampsilini)

The genus Epioblasma consists of 20 species and eight subspecies, of which 15 species and four subspecies are presumed or probably extinct. Remaining taxa are considered endangered or threatened largely due to habitat destruction or modification. We conducted a molecular genetic study on all known extant populations of two federally endangered freshwater Epioblasma species: the tan riffleshell, E. florentina walkeri (Wilson & Clark, 1914), and oyster mussel, E. capsaeformis (Lea, 1834), to determine the extent of genetic variation within and among populations of the two species. Mitochondrial DNA sequence data from two protein-coding genes (COI and ND1) failed to differentiate E. capsaeformis from E. f. walkeri. Molecular variation within and between the two species does not exceed limits observed within Epioblasma brevidens, although substantial genetic differences are observed among E. brevidens, E. triquetra and E. capsaeformis + E. florentina walkeri. Although data do not support the recognition of the two taxa as separate phylogenetic species, they still warrant endangered status due to the fact that few reproducing populations are known. Life history and population biology studies have already been conducted on the single known extant reproducing population of nominal E. f. walkeri. However, similar comparative studies should be conducted on the different mantle-pad morphs of nominal E. capsaeformis populations to provide valuable data for more effective management of the recovery of the phylogenetic species and to further test our hypothesis.