Genetic Identity of the Least Brook Lamprey (Lampetra aepyptera) in Indiana

Abstract

The Least Brook Lamprey (Lampetra aepyptera) is a common inhabitant of small streams throughout the southeast United States and reaches its northern-most extent near the boundary of the glacial till plains of southern Indiana, Ohio, and western Pennsylvania. Previous genetic studies found that populations from eastern Kentucky and Ohio were distinct from other populations of L. aepyptera, suggesting that these populations from the upper Ohio River basin were isolated in their current locations well before the Pleistocene. However, samples from Indiana (or elsewhere in the lower Ohio River basin) were not included in these studies. As the modern Ohio River system was established in the late Pleistocene (or after), samples from Indiana will be critical to our understanding of the historical factor(s) giving rise to the distribution of L. aepyptera in the Ohio River basin. Sequence variation of the mitochondrial NADH dehydrogenase subunit 3 gene from specimens of L. aepyptera collected from across its distribution were examined to better understand the phylogeographic position of the Indiana populations. Specimens collected from southern Indiana, Illinois, and the Green River of Kentucky (the lower Ohio River basin) formed a well-supported monophyletic group with specimens collected from the upper Ohio River basin. Deeper relationships within the species remain unresolved. The Ohio River clade shows evidence of reduced genetic heterogeneity relative to more southerly populations, consistent with an assemblage of populations that has recently expanded. Our results suggest that the contemporary distribution of L. aepyptera in the Ohio River basin was established after the integration of the modern Ohio River system in the late Pleistocene.