Comparative Population Genetics of Bighead and Silver Carps: Invasion Fronts Approaching the Great Lakes

Of top ecological concern is the impending invasion of bighead carp Hypophthalmichthys nobilis and silver carp H. molitrix (collectively “Asian carps") populations that are rapidly spreading throughout much of the Mississippi River watershed, with three primary fronts now located at the gates of the Great Lakes. However, almost nothing is known of the fundamental population genetic variability underlying the spread of Asian carps in North America. Here, we present preliminary results of a comprehensive characterization of Asian carps population genetics from two invasion front populations: (1) the Illinois River north of Peoria, IL (approaching southern Lake Michigan), and (2) the Wabash River, Lafayette, IN (approaching the Maumee River/Western Lake Erie system). We analyze their comparative population genetic structures based on sequence data from two mtDNA genes - COI (barcode) and cyt-b - and 10 nuclear DNA microsatellite loci. We additionally use microsatellite loci distinguishable between bighead and silver carp to assess and characterize the extent of hybridization between bighead and silver carp at invasion front populations, which may significantly affect their ecology, invasiveness, and success in new habitats. Initial analyses show F_ST values (α=0.05) for COI and cyt-b are not significant among silver carp populations between the two invasion front sites, and levels of genetic diversity are high. No bighead carp mtDNA parent sequences are identified in Wabash River silver carp samples. Future research will include a third invasion front population (the northward extent of the Mississippi River), populations from three longer established North America locations, and a native population in Asia. This research aims to provide managers with important genetic baseline tools towards combatting the invasion and mitigating its effects.