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Dryad

Conservation genetic assessment of the paleback darter (Etheostoma pallididorsum), a narrowly distributed endemic in the Ouachita Highlands, Arkansas, USA

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Jun 15, 2021 version files 50.27 KB

Abstract

  1. The Paleback Darter is considered imperiled and has recently been petitioned for listing under the Endangered Species Act. Prior allozyme-based studies found evidence of small effective population size, warranting conservation concern. The objective of this study was to assess population dynamics and the phylogeographic history of the Paleback Darter, using a multilocus microsatellite approach and mitochondrial DNA.
  2. The predictions of this study were that Paleback Darter populations will exhibit low genetic diversity and minimal gene flow; population structure will correspond to river systems where samples are derived; the reservoir dams impounding the reaches between the Caddo and Ouachita rivers would serve as effective barriers to gene flow; and the Caddo and Ouachita rivers are reciprocally monophyletic.
  3. Microsatellite DNA loci revealed significant structure among sampled localities (global Fst = 0.17, P < 0.001), with evidence of two distinct populations representing the Caddo and Ouachita rivers. However, Bayesian phylogeographic analyses resulted in three distinct clades, Caddo River, Ouachita River, and Mazarn Creek. Divergence from the most recent ancestor shared among the river drainages was estimated at 60-KYA. Population genetic diversity was relatively low (He = 0.65; mean alleles per locus [A] = 6.26), but comparable to close relatives, Slackwater Darter (He = 0.65; A = 6.74) and Tuscumbia Darter (He = 0.57; A = 5.53).
  4. These results have conservation implications for Paleback Darter populations and can be informative for other headwater specialist species. Like other headwater species with population structuring and relatively low genetic diversity, persistence of Paleback Darter populations is likely tied to persistence and connectivity of local breeding and non-breeding habitat. These results do not raise conservation concern for a population decline; however, the restricted distribution and endemic status of the species still renders Paleback Darter populations vulnerable to extirpation or extinction.