Evidence of Introgressive Hybridization in the GenusStizostedion: Interspecific Transfer of Mitochondrial DNA between Sauger and Walleye

Abstract

The mitochondrial genotypes of walleye (Stizostedion vitreum) and sauger (Stizostedion canadense) are readily differentiated, permitting an analysis of the incidence of hybridization between the taxa. We provide evidence that introgression of sauger into walleye has occurred: two female walleye collected from Lake Simcoe contained a mitochondrial genome identical to that of sauger. Not only were these two fish morphologically indistinguishable from typical walleye, they were homozygous for the diagnostic alleles characteristic of walleye at the Mdh-3 and Pgm-1 allozyme loci. Sauger have not been recorded in Lake Simcoe, but a few individuals may have been inadvertently introduced during stocking programs and introgressed with walleye due to a lack of conspecific mates.