Population genetics of the freshwater mussel, Amblema plicata (Say 1817) (Bivalvia: Unionidae): Evidence of high dispersal and post-glacial colonization

Abstract

Over 70% of North American freshwater mussel species (families Unionidae and Margaritiferidae) are listed as threatened or endangered. Knowledge of the genetic structure of target species is essential for the development of effective conservation plans. Because Ambelma plicata is a common species, its population genetic structure is likely to be relatively intact, making it a logical model species for investigations of freshwater mussel population genetics. Using mtDNA and allozymes, we determined the genotypes of 170+ individuals in each of three distinct drainages: Lake Erie, Ohio River, and the Lower Mississippi River. Overall, within-population variation increased significantly from north to south, with unique haplotypes and allele frequencies in the Kiamichi River (Lower Mississippi River drainage). Genetic diversity was relatively low in the Strawberry River (Lower Mississippi River drainage), and in the Lake Erie drainage. We calculated significant among-population structure using both molecular markers (A.p. F st = 0.15, h st = 0.12). Using a hierarchical approach, we found low genetic structure among rivers and drainages separated by large geographic distances, indicating high effective population size and/or highly vagile fish hosts for this species. Genetic structure in the Lake Erie drainage was similar to that in the Ohio River, and indicates that northern populations were founded from at least two glacial refugia following the Pleistocene. Conservation of genetic diversity in Amblema plicata and other mussel species with similar genetic structure should focus on protection of a number of individual populations, especially those in southern rivers.

Phylogeographic and population genetic analyses reveal Pleistocene isolation followed by high gene flow in a wide ranging, but endangered, freshwater mussel

“…There were more haplotypes in this species compared with other endangered mussels (Zanatta and Murphy, 2008), but about the same as in other widespread species (Elderkin et al, 2007). Because most haplotypes were only 1 bp different, and both nucleotide diversity and among-population …”

“…Polymerase chain reaction and sequencing of a 678-bp region of the COI gene was performed as in Elderkin et al (2007), except BigDye v3.1 (Applied Biosystems, Foster City, CA, USA) was used for sequencing reactions. An ABI Genetic Analyzer produced sequences that were aligned visually in DNADY-NAMO (Blue Tractor Software, Llanfairfechan, UK).…”

“…ARLEQUIN was also used to calculate mean nucleotide diversity (p) within each population. To test for a latitudinal gradient in genetic diversity (Elderkin et al, 2007), the number of haplotypes, nucleotide diversity, and mean number of base pair differences within populations were regressed with latitude using linear regression analysis.…”

“…Despite this close relationship, most phylogeographic studies of mussels have been limited to endangered species with either very small population sizes or limited geographic ranges (Roe et al, 2001). Several recent studies of phylogeography of widespread mussel and fish species have found evidence that species colonized previously glaciated drainages, such as the upper Mississippi River and northern Atlantic coastal drainages, from multiple refugia (Bernatchez and Wilson, 1998;Burdick and White, 2007;Elderkin et al, 2007). Populations in glaciated regions typically have less genetic diversity than those in southern unglaciated areas.…”

Molecular phylogeny of the Nearctic and Mesoamerican freshwater mussel genus Megalonaias

“…Individuals from the most northern and southern portions of the distribution (i.e., Minnesota to Guatemala) differed by a less than 1% average COI p-distance and had identical ITS1 haplotypes ( Table 2). The COI sequence divergence within Megalonaias is lower than the intraspecific diversity of many other more geographically restricted amblemine species (Roe & Lydeard, 1998;Grobler et al, 2006;Burdick & White, 2007;Elderkin et al, 2007;Inoue et al, 2013). Despite having relatively low genetic divergence in comparison to many other amblemines, there is significant genetic structure associated with the five a priori geographic regions (AMOVA P \ 0.001).…”