Discovery of genetically distinct sympatric lineages in the freshwater mussel cyprogenia aberti (Bivalvia: Unionidae)

The western fanshell, Cyprogenia aberti, occurs in the Central Highlands region of North America and is the only congener of the federally endangered fanshell, C. stegaria. Due to a reduction in range size and local extirpations, extant populations of C. aberti have become increasingly isolated. Consequently, C. aberti has been the focus of numerous conservation efforts, yet no work has examined the degree of genetic variation among the species' disjunct populations. Phylogenetic analyses of nucleotide sequences from two mitochondrial gene portions (CO1 and ND1) revealed results important to the conservation management of C. aberti. First, phylogenetic analyses do not support a monophyletic C. aberti. Second, C. aberti is comprised of as many as five independent lineages, one of which includes the federally endangered C. stegaria. Third, analysis recovered two genetically distinct sympatric lineages of C. aberti in the Ouachita River Drainage. These phylogenetic results suggest that the five distinct evolutionary lineages of C. aberti should be managed as separate conservation units. This study illustrates why it is critical to evaluate genetic variability in endangered and threatened 'species' prior to implementing a recovery program. These data also reveal the value of assessing biological diversity of nonimperiled taxa before populations are extirpated and valuable genetic data necessary for reconstruction of evolutionary relationships is lost.