Genetic analysis of the rapid expansion of banded killifish in the Great Lakes Region.

Banded killifish range from the Atlantic coast through the Great Lakes and upper Midwestern states. The eastern subspecies occupies the Atlantic coast and inland to Lakes Ontario and Erie, whereas the western subspecies ranges from Lake Erie west through the upper Midwest. Western banded killifish were often collected in kettle lakes in the southern Lake Michigan basin, but declined throughout the 1900s. Since the early 2000s, an expansion of banded killifish into the Illinois and Mississippi rivers prompted investigations into which subspecies is causing the spread. We have morphological and mtDNA analyses that suggest the non-native eastern subspecies has expanded its range. The invasion of eastern banded killifish could negatively impact the native western subspecies through mechanisms including hybridization and competition. It is important to protect the native western subspecies while understanding how this invasion could influence aquatic communities in the Great Lakes region.