GENETIC-RELATIONSHIPS AMONG THE TORRENT SUCKERS, GENUS THOBURNIA

Population samples of the three species of the tetraploid catostomid genus Thoburnia were electrophoretically studied to detect isozyme variability resolving the products of 54 alleles encoded by 34 presumptive loci. Species of Thoburnia express only about one-third of their loci in duplicate suggesting a high level of evolutionary advancement within the Catostomidae. Thoburnia hamiltoni and T. rhothoeca are phenetically close compared to T. atripinne. Cladistic analyses of the genetic data reveal that T. rhothoeca exhibits a relatively high degree of plesiomorphy while T. hamiltoni and T. atripinne represent extremes of separate lineages. A phylogenetic treatment of the genetic data yields a hypothetical phylogeny congruent with that based on morphological criteria. © 1979.