Using Ancient DNA to Solve the Mystery of the Extinct Blue Pike Sander Vitreus Glaucus Hubbs

Loss of unique taxa and declining species diversity are growing problems that threaten ecosystems worldwide, often accompanying exploitation, habitat alteration, and pollution. The North American Great Lakes – the world’s largest freshwater ecosystem - once housed a putatively unique percid fish taxon in Lake Erie, termed the blue “pike” Sander vitreus glaucus, until its popular and abundant fishery crashed in the early 1960s. The blue pike was declared extinct and Lake Erie was termed ecologically “dead” in the 1970s due to pollution. Lake Erie has since recovered, and supports an abundant walleye fishery today, but the blue pike has not been seen again. It has long been questioned whether the blue pike was a distinct species, subspecies, or an ecophenotypic variant of the “yellow” walleye Sander vitreus vitreus. DNA sequencing of the mtDNA control region and analyses of nuclear DNA microsatellites of historic material, offer the means to understand the blue pike’s evolutionary and biogeographic relationships, and determine whether it genetically hybridized with yellow walleye. We analyzed 20 of the blue pike paratypes described by Hubbs in 1926 in comparison with genetic and morphological data of 20 historic walleye from Lake Erie, along with 800+ modern walleye from Lake Erie and throughout their North American range. Results indicate no diagnostic genetic or morphological characters differences between the blue pike and yellow walleye, with some slight sampling trends in their interorbital distances and head widths. In contrast, walleye show considerable population genetic differences among spawning locations and geographic regions across their range. Our results indicate that the extinct blue pike did not merit taxonomic distinction.