Molecular Genetics and Phylogeny of Bigmouth Shiner, Notropis dorsalis

The study of North American freshwater ichthyofauna reveals a diversity shaped by the continent\u27s geologic past and the extensive effects of Pleistocene glaciation on river systems. Ericymba dorsalis (Bigmouth 69 Shiner) is a minnow species with a broad distribution in the Mississippi River basin from Wyoming to New York. Despite exhibiting consistent morphological features across its range, the species\u27 widespread northern distribution suggests the potential existence of multiple, genetically distinct lineages. This research tested the hypothesis that separate drainage systems harbor genetically distinct groups of E. dorsalis. Our results identified five clades, each associated with major drainages. Populations of the Missouri River, upper Mississippi River, and Illinois River, respectively, grouped into three clades with divergence of 1.3-1.6%, indicating a Pleistocene origin. Three disjunct populations located in Great Lakes tributaries in western Michigan, Ohio, and New York, respectively, formed a fourth clade, and population samples from the Allegheny River in Pennsylvania formed a fifth clade. The divergence of the Great Lakes and Allegheny clades from the western clades ranged 4.3-5.3%, suggesting an early Pleistocene or Pliocene origin. This pattern of distribution underscores the role of vicariance biogeography during Pleistocene glaciation, on the current distribution of genetic diversity in E. dorsalis