Microsatellite DNA analysis of parapatric lamprey (Entosphenus spp.) populations: implications for evolution, taxonomy, and conservation of a Canadian endemic

Parapatric freshwater and anadromous parasitic lampreys (Petromyzontiformes) from southwestern Vancouver Island, British Columbia, have been described as distinct taxa (Vancouver lamprey (Entosphenus macrostomus (Beamish, 1982)) and Pacific lamprey (Entosphenus tridentatus (Richardson, 1836)), respectively), using morphology, life history, and physiology. We tested for genetic differentiation at microsatellite DNA loci between these taxa and similar freshwater parasitic lampreys from two other lakes. The number of alleles and expected heterozygosity averaged 3.8 and 0.50, respectively, across loci and populations, and anadromous populations were more variable than freshwater populations. Population subdivision was moderate (F-ST = 0.096, P < 0.001) and 3% of the total variation was found between taxa and 1.7% was found among populations within taxa (both P < 0.001). Parapatric freshwater and anadromous parasitic lampreys separated by a maximum of 40 km were more distinct (mean F-ST = 0.042) than were anadromous populations located 800 km from one another (mean F-ST = 0.012). Localities within lakes with parasitic freshwater lampreys, however, showed little differentiation (F-ST = 0.0-0.08). Our data support recognizing E. macrostomus and E. tridentatus as distinct species, but similar levels of differentiation between these taxa and other freshwater parasitic lampreys suggest a species complex where the taxonomy remains unclear.