INVESTIGATIONS INTO THE PHYLOGENETIC RELATIONSHIPS OF FRESHWATER PEARL MUSSELS (BIVALVIA: MARGARITIFERIDAE) BASED ON MOLECULAR DATA: IMPLICATIONS FOR THEIR TAXONOMY AND BIOGEOGRAPHY

The phylogenetic relationships among selected members of the family Margaritiferidae are investigated using sequence data from five molecular markers. Parsimony analyses of the data support the recognition of those nominal species for which multiple samples were included in the study (Margaritifera margaritifera, M. laevis, M. falcata and M. auricularia). Although not always strongly supported, the following relationships were consistently recovered: (Cumberlandia + Margaritifera auricularia), (M. falcata (M. marrianae + M. laevis)) and to a lesser degree (Dahurinaia dahurica + M. margaritifera). The molecular phylogeny indicates that the taxonomy of the group is in need of revision since the genus Margaritifera is not monophyletic and a new taxonomy by Smith (2001) is not supported. A complicated pattern of biogeography was suggested by the three clades of Old World + New World species. It is difficult to determine whether this pattern is a reflection of extinction and contraction of an ancient, formerly widespread margaritiferid fauna, peripheral isolation of formerly widespread taxa, fish host dispersal, or even host switching.