Genetic diversity in the threatened freshwater mussel Lampsilis powellii

North America is home to the greatest share of the world’s freshwater
mussel diversity; however, over 70% of its ~300 species are endangered or
threatened. Lampsilis powellii, the Arkansas Fatmucket, is endemic to
Arkansas and now restricted to upstream reaches of the Ouachita and Saline
rivers, but the species is declining within this small range. Conservation
actions such as augmenting or reintroducing populations may be necessary,
but they require knowledge of the distribution of genetic variation within
and among extant populations. We analyzed population structure between the
South Fork Ouachita River and Saline River using a 607 base pair region of
the mitochondrial COI gene and 14 microsatellites designed for Lampsilis
abrupta. COI sequences showed little variation and the most common
haplotype was present in both rivers. Our mtDNA sequences were
indistinguishable from those of L. siliquoidea deposited on GenBank, but
we were unable to make conclusions about the taxonomic distinctiveness of
L. powellii. Microsatellites showed heterozygote deficiency for most loci
and revealed little evidence of population structure between the two
rivers. Overall, our results show low genetic diversity in L. powellii,
which may reflect its small population size due to its long history of
geographic isolation compounded by anthropogenic habitat destruction and
fragmentation. Further genetic analyses of lampsiline taxa is needed to
establish species limits for Lampsilis in the Interior Highlands.