Phylogeography of the tailed frog (<i>Ascaphus truei</i>) in British Columbia

Abstract

The tailed frog (Ascaphus truei) is highly philopatric, with naturally disjunct populations. To infer the histor - ical pattern of range expansion and contraction in A. truei of British Columbia (B.C.), we conducted a randomly ampli- fied polymorphic DNA (RAPD) survey, using 16 primers, of 469 individuals sampled from 22 populations in four regions. Genetic distances, based on 169 putative RAPD loci, clustered populations into three clear groups: mid/north-coastal B.C., south-coastal B.C., and interior B.C. The interior populations were the most distinct group, but their genetic dis - tance from other groups equals that expected from isolation by physical distance alone, as opposed to taxonomic differ- entiation. FST values within coastal regions were moderately low (0.02-0.05) but were high in the interior (0.12) and across all populations (0.18). Within the mid/north-coastal and south-coastal regions, genetic distance showed no rela - tionship with physical distance, while among regions and within the interior region there was a strong relationship. Gene diversity varied significantly among regions, with both the interior and south-coastal populations showing about 25% less diversity than the mid/north-coastal populations. These data indicate a complex history of geographic restric - tions to multiple refugia, followed by various types of range expansion. The implications of these results for conserva - tion efforts in this species are discussed.