The influence of historical and contemporary landscape variables on the spatial genetic structure of the rainbow darter (Etheostoma caeruleum) in tributaries of the upper Mississippi River

Abstract

Evaluating spatial genetic patterns is an important method to help inform management efforts for the conservation of native fishes. However, the present study demonstrates that it is vital to consider life history, distribution, and historical processes when interpreting the spatial distribution of genetic diversity. This study examined genetic variation in populations of the Rainbow Darter, Etheostoma caeruleum, in tributaries of the upper Mississippi River in northeast Iowa in order to understand the influence of landscape alteration at multiple temporal scales. The diversity and distribution of fishes in this region are influenced by historical geologic and climatic events, and recent, intensive human activities, making this an excellent site for an investigation of this type. Landscape genetic analyses of eight microsatellite loci from 14 localities detected a single genetic population. The amount of genetic diversity observed within localities and drainages was high, but the distribution of genetic variation was almost uniform across the study area. There was no evidence of population subdivision at any spatial scale. Based on what is known about the life history of the Rainbow Darter and the geological history of the region, the best explanation for these results is that historical processes had a more pronounced influence on the observed genetic variation than contemporary impacts. Specifically, the genetic signature supports a conclusion of population expansion into the region following the retreat of glacial advances during the Pleistocene.