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

Abstract

Freshwater organisms of North America have had their contemporary genetic structure shaped by vicariant events, especially Pleistocene glaciations. Life history traits promoting dispersal and gene flow continue to shape population genetic structure. Cumberlandia monodonta, a widespread but imperiled (IUCN listed as endangered) freshwater mussel, was examined to determine genetic diversity and population genetic structure throughout its range. Mitochondrial DNA sequences and microsatellite loci were used to measure genetic diversity and simulate demographic events during the Pleistocene using approximate Bayesian computation (ABC) to test explicit hypotheses explaining the evolutionary history of current populations. A phylogeny and molecular clock suggested past isolation created two mtDNA lineages during the Pleistocene that are now widespread. Two distinct groups were also detected with microsatellites. ABC simulations indicated the presence of two glacial refugia and post-glacial admixture of them followed by simultaneous dispersal throughout the current range of the species. The Ouachita population is distinct from others and has the lowest genetic diversity, indicating that this is a peripheral population of the species. Gene flow within this species has maintained high levels of genetic diversity in most populations; however, all populations have experienced fragmentation. Extirpation from the center of its range likely has isolated remaining populations due to the geographic distances among them.

Past climate change drives current genetic structure of an endangered freshwater mussel species

“…We followed procedures for conditions for PCR, sequencing and post‐sequencing analyses described in Inoue et al . ().…”

“…We used previously published procedures for fragment analyses, allele scoring and assignment of integer numbers to DNA fragment sizes (Inoue et al . ).…”

“…; Inoue et al . ) in order to evaluate type I and type II error rates. To assess precision of parameter estimation, we computed the relative median of the absolute error (RMAE; Cornuet et al .…”

“…; Inoue et al . ). Studies of evolutionary responses to vicariant events are especially timely, given rapid changes in ecological conditions due to climate change and anthropogenic disturbance.…”

A comparison of genetic diversity and population structure of the endangered scaleshell mussel (Leptodea leptodon), the fragile papershell (Leptodea fragilis) and their host-fish the freshwater drum (Aplodinotus grunniens)

“…Those authors raised the possibility that observed species differences in gene flow between rivers was due to differences in host vagility (different mussel species utilizing different fish species as hosts), but such and explanation is not valid in this case as both mussels share the same host fish. Inoue et al (2013) noted that since freshwater mussels and their hosts live in linear river systems, mussels with vagile hosts can be dispersed across great distances which would results in low or no population differentiation. Aplodinotus grunniens, like brown trout, has higher mobility than does the common logperch.…”