• Kelly, Morgan W.
  University of Maine Graduate School
  

The tidewater mucket (Leptodea ochracea)  and yellow lampmussel (Lampsils cariosa) are two freshwater mussel species in serious need of conservation, as they are declining throughout most of their Atlantic slope ranges. Both species are listed as Threatened in Maine, and as endangered, threatened, of special concern, or species at risk in most states and provinces throughout their ranges, which extend from Nova Scotia to Georgia. Because freshwater mussels rely on fish hosts for movement of their larvae, barriers to the movement of fish hosts, such as fragmentation by dams, may indirectly affect population genetic structure in mussels. An understanding of population genetic structure for L. ochracea and L. cariosa in Maine is important to delineate management units at the state level and may illuminate some of the landscape level factors affecting population structure in both species. I used microsatellite loci originally developed for Lampsilis abrupta to assess population level genetic variation for L cariosa and L ochracea within and among three river drainages in Maine. Seven of these loci were used to assess population structure of L. Cariosa, but only three of the loci that amplified in L ochracea were polymorphic. There was evidence for null alleles at some loci, but consistently in results across loci indicated that my overall findings were robust. Both species had significant genetic differences among populations. Significant differences were observed among populations within and among drainages for L. cariosa. By contrast, within, but not among, drainage differences were observed for L ochracea. Although L. Cariosa exhibited significant isolation by distance, there was no correlation between genetic distance and the number of intervening dams for either species after correcting for the effects of geographic distance. these results will be valuable in developing management plans at the state level, especially in light of impending dam removals, which are likely to require translocations of both species. Where translocations become necessary, I recommend that they occur among least divergent populations, if ecological conditions permit.