Mitochondrial gene arrangement and the evolution, systematics, and conservation of freshwater mussels (Bivalvia: Unionidae) of North America

North American freshwater mussels in the family Unionidae are one of the most endangered groups of organisms in the world. Accurate identification of biological diversity within this group is a critical first step to successful conservation and recovery efforts. Phylogenetic analyses of mitochondrial (mt) DNA sequence data have been successfully used to identify evolutionary lineages and reconstruct genealogical relationships of unionid taxa. However, these studies have been limited to a few gene portions, which utilize less than one tenth of the mt genome. In the first study, the complete mt genome was sequenced and gene order was determined for the North American species Lampsilis ornata. The unique gene arrangement of Lampsilis was compared to five other bivalves in a phylogenetic framework. Although gene order is highly variable among bivalves, when optimized on an independently derived phylogenetic hypothesis it provides phylogenetically informative character states that can infer evolutionary changes within mt genome content and supports phylogenetic relationships. The second study compares morphologically diagnosed species and species groups within the genus Quadrula to a molecular phylogeny based on nad1 sequence data. Analysis recovered three monophyletic species groups within the genus (quadrula, pustulosa, and metanvera) and a Quadrula clade that included all currently recognized Quadrula species and three non-Quadrula taxa ( Fusconaia succissa, Quincuncina infucata, and Tritogonia verrucosa). The taxonomic description of the genus Quadrula should be expanded to include these non-Quadrula species. The final study phylogenetically examines nucleotide sequences of two mitochondrial (cox1 and nad1) and one nuclear (ITS-1) gene portions to determine genetic diversity and relationship among populations of Cyprogenia aberti in the Central Highlands region of North America. Phylogenetic analyses of these data do not support a monophyletic C. aberti. Genetic analyses reveals as many as five species, including the federally endangered C. stegaria, comprise C. aberti. These five distinct evolutionary lineages should be managed as separate conservation units. This study illustrates the extraordinary value of assessing biological diversity of non-imperiled taxa before populations are extirpated and valuable genetic data necessary for reconstruction of evolutionary relationships is lost.