Genetic Distribution and Diversity of the Johnny Darter ('Etheostoma Nigrum', Rafinesque) in the Upper Midwest

摘要

This novel study examined the existing phylogeography of Etheostoma nigrum (Johnny darter, Rafinesque) in the Upper Midwest. Four microsatellite loci were chosen to examine eight populations of E. nigrum, a non-migratory, benthic fish, from three drainage basins: the Red River of the North, the upper Missouri River, and the upper Mississippi River. These systems provide an excellent opportunity for phylogeographic studies as they have only been recently available to colonization by ichthyofauna. we applied four microsatellite loci to examine population structure within and among these major watersheds. Using AMOVA, strong evidence of a watershed effect was observed with 31% of the genetic variance among watersheds. Variance between populations within drainages accounted for 9% of the total variation. This observation was further supported using a Bayesian analysis which identified five well-supported assemblages which roughly agreed with watershed assignment. One notable exception to this pattern was observed for Lake Ida. This isolated lake is located in the Red River drainage; however, the population more closely aligned with populations from the upper Mississippi River. Because Johnny darters show considerable geographic genetic structure, they provide a good model to compare with other species that have been translocated within and among drainages.