The evolution, population genetics, and conservation of lampsiline freshwater mussels (Bivalvia: Unionoida: Lampsilini)

The biodiversity of freshwater mussels is diminishing at a nearly unprecedented pace, with many species being added to legally protected lists. In response to this imperilment, this dissertation investigates the evolution and population genetics of mussels from the tribe Lampsilini of freshwater mussels.;Species in the Order Unionoida require a host, usually a fish, to complete their life cycle. Females of most species show adaptations that increase the chances of glochidia larvae contacting a host. Using a suite of mitochondrial DNA sequences, a phylogenetic hypothesis for the evolution of the lampsiline species was created to test the evolution of host attracting structures and behaviours.;To assist in managing lampsiline species, population-level studies of the imperiled Northern Riffleshell (Epioblasma torulosa rangiana), Snuffbox (E. triquetra) and Wavy-rayed Lampmussel ( Lampsilis fasciola) were conducted to test possible routes of post-glacial redistribution and for the existence of conservation units, population structure and genetic diversity. Analyses were made using mitochondrial DNA sequences and microsatellite loci, including six that were newly developed. For E. t. rangiana, mtDNA sequence data did not indicate significant geographic structure among populations. However, allelic data from the microsatellite loci revealed highly significant population structuring. For E. triquetra, the results indicated the occurrence of three glacial refugia: the Tennessee River, rivers south of the Ozark Crest, and the lower Ohio River drainage near the confluence with the Mississippi. The four sympatrically-occurring mantle display-types could not be distinguished genetically via an assessment of microsatellite DNA loci. Within-drainage gene flow was high and sampling localities within drainages displayed panmixia. For all species, efforts in artificial propagation and possible translocations programs to reintroduce or augment populations should be made to maintain significant levels of genetic variation while maintaining distinctiveness.;It is necessary to investigate alternative ways to conserve the biological and genetic diversity of imperiled unionoids within the framework of conservation law. In order to clarify definitions and concepts for conservation units for unionoids, studies of unionoid evolution, population genetic structure, cryptic species, and taxonomic conflict are discussed. From this synthesis of studies, recommendations are made for the appropriate usage of these units under endangered species legislation.