Assessment of genetic diversity and structure among populations of Epioblasma triquetra in the Laurentian Great Lakes drainage

Caitlin E. Beaver, Daelyn A. Woolnough, David T. Zanatta

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7 Scopus citations


The endangered freshwater mussel (Bivalvia:Unionidae) Epioblasma triquetra, or Snuffbox, has the largest distribution of any extant species in its highly threatened genus. The Laurentian Great Lakes populations of E. triquetra are among the most important remaining strongholds. Genetic data are needed to inform managers how best to conserve and, where necessary, restore populations in the region. We used genotypes from 8 polymorphic microsatellite loci to examine the genetic diversity and structure of the 12 locations (n 5 277 individuals) where E. triquetra are known to persist in the Great Lakes region. Similar levels of heterozygosity and allelic richness were observed in these populations. Only 1 of the 12 sampling locations (Embarrass River, Wisconsin) showed any evidence of a recent bottleneck and none showed evidence of significant inbreeding. Genetic structure followed the geographic distribution of the sampling locations in the 3 major drainages sampled: the Green Bay drainage, Wisconsin; the Grand River drainage, Michigan; and the Huron-St Clair-Erie corridor. Epioblasma triquetra in rivers that drain into the Huron-St Clair-Erie corridor showed some substructure in the Clinton, Ausable, and Sydenham rivers. The genetic structure across the Great Lakes region is consistent with multiple post-glacial colonization events by E. triquetra into the Great Lakes after the retreat of the Wisconsin ice sheet. We found evidence that Lake Michigan acts as a physical barrier to gene flow based on Monmonier's algorithm and comparisons of hierarchical AMOVAs using AICc tests. All analyses supported entry of E. triquetra into the Great Lakes region via multiple colonization routes as the best fitting hypothesis to the genetic data. The clear pattern of genetic structure and diversity observed for E. triquetra in the Great Lakes region suggests that conservation efforts and management decisions should take genetic profiles into context before allowing for admixture among genetic populations via translocations or hatchery propagation of juveniles.

Original languageEnglish
Pages (from-to)527-542
Number of pages16
JournalFreshwater Science
Issue number3
StatePublished - Sep 1 2019


  • Freshwater mussels
  • Genetic diversity
  • Genetic structure
  • Laurentian Great Lakes
  • Microsatellites
  • Population genetics
  • Post-glacial colonization


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