Geographic variation in morphology of Aphredoderus sayanus (Gilliams) (Teleostei: Aphredoderidae)

The pirate perch, Aphredoderus sayanus (Gilliams), occurs in Atlantic Slope, Gulf Slope, and Mississippi Valley rivers. The populations on the Atlantic Slope have been considered subspecifically distinct from the populations of the Mississippi Valley, while the Gulf Slope populations were considered intermediate. These subspecies distributions were based on the distribution of the subspecies of Esox americanus Gmelin, which has a similar distribution of A. sayanus. Recently it has been proposed that the subspecies of A. sayanus not be recognized until a complete study of the geographic variation has been completed. The purpose of this study was to determine the amount of geographic variation and the taxonomic status of the populations from the three geographic areas.;Twenty-seven characters were examined on 1,211 individuals. Principal component analysis (PCA) was used to analyze these data. Many of the characters, when examined separately, exhibited clinal or discordant geographic trends. The Mississippi Valley populations generally had the highest values for the serial elements. The lack of correlation with environmental data indicated that most of the clinal patterns were not solely due to environmental differences. Principal component analysis using the meristic data yielded two geographic groups, Atlantic Slope populations and the Mississippi Valley populations. The Gulf Slope populations were intermediate to these two populations. When the mensural data were analyzed using sheared principal components there still was no overlap between the Atlantic Slope populations and the Mississippi Valley populations, whereas the amount of overlap with the Gulf Slope populations increased. Based on the above findings and the zoogeography of the pirate perch the two subspecies, Aphredoderus sayanus sayanus and Aphredoderus sayanus gibbosus, are recognized. A. s. sayanus occurs on the Atlantic Slope south to the Saint Marys River. The populations from the Saint Marys River west to the Pearl River should be considered intergrades. A. s. gibbosus occurs on the Gulf Slope west of the Mississippi River, in the Mississippi Valley, and in the Great Lakes.