Molecular Phylogeny Of The Freshwater Mussel Family Dreissenidae

The bivalve family Dreissenidae contains some of the most economically and ecologically important fresh and brackish-water mollusk species. There has been much uncertainty surrounding phylogenetic resolution for members of Dreissenidae. The lineage is believed to have originated 83.6 million years ago in the Tethys and Paratethys seas. Three extant dreissenid genera are currently recognized, Dreissena, Mytilopsis, and Congeria. However, in 2012, an un-described mussel was discovered in the Xingu River, a tributary of the Amazon River in central Brazil. The objective of this study was to determine the evolutionary history of the unknown South American dreissenids (USADs) and determine their proper taxonomic placement. I examined phylogenetic relationships among 10 described species within Dreissenidae and 6 related outgroups using nuclear and mitochondrial genes, a molecular clock analysis and a comparative analysis of life history characteristics to determine the evolutionary history of these enigmatic bivalves. Recent analyses suggest that these bivalves may comprise a distinct genus within Dreissenidae containing three species. My analyses support this hypothesis and revealed that the common ancestors of today’s USADs first diverged as a distinct lineage ~27.1 MYA. Due to phylogenetic analyses, genetic distance, and life history characteristics I believe USADs are sister taxa to Congeria.