Inter-population genetic variation in the freshwater leech Nephelopsis obscura in relation to environmental heterogeneity

Abstract

Genetic variation among three populations of the freshwater leech, Nephelopsis obscura was examined. Fixed genetic differences occurred among populations at four protein-coding genes. Despite the higher probability of dispersal between Stephenson's Pond in the Alberta prairie-foothills zone and the Alberta Rocky Mountain pond (80 km apart) and the lower probability of dispersal between these two ponds and the Uinta Mountain population in Utah (1 200 km away), the Alberta Rocky Mountain population differed from the Utah Uinta Mountain population at only one locus while both populations differed at five loci from the Stephenson's Pond population. All four enzymes showing differences between populations are involved in anaerobic pathways. It is hypothesized that genetic similarities and differences are correlated with the dissolved oxygen regimes acting as a selective force rather than geographical distance between populations.