biostudies-literatureUnknown12(3)Mosher CMReconstruction of historical relationships between geographic regions within a species' range can indicate dispersal patterns and help predict future responses to shifts in climate. <i>Ascaphus truei</i> (coastal tailed frog) is an indicator species of the health of forests and perennial streams in the Coastal and Cascade Mountains of the Pacific Northwest of North America. We used two genetic techniques-microsatellite and genotype-by-sequencing (GBS)-to compare the within-region genetic diversity of populations near the northern extent of the species' range (British Columbia, Canada) to two geographic regions in British Columbia and two in Washington, USA, moving toward the core of the range. Allelic richness and heterozygosity declined substantially as latitude increased. The northernmosEcology and evolutione8716https://www.ebi.ac.uk/biostudies/studies/S-EPMC8931771biostudies-literatureReduced genetic diversity associated with the northern expansion of an amphibian species with high habitat specialization, <i>Ascaphus truei</i>, resolved using two types of genetic markers.PMC8931771Mosher CMMurray BWJohnson CJfalseReduced genetic diversity associated with the northern expansion of an amphibian species with high habitat specialization, <i>Ascaphus truei</i>, resolved using two types of genetic markers.Reconstruction of historical relationships between geographic regions within a species' range can indicate dispersal patterns and help predict future responses to shifts in climate. <i>Ascaphus truei</i> (coastal tailed frog) is an indicator species of the health of forests and perennial streams in the Coastal and Cascade Mountains of the Pacific Northwest of North America. We used two genetic techniques-microsatellite and genotype-by-sequencing (GBS)-to compare the within-region genetic diversity of populations near the northern extent of the species' range (British Columbia, Canada) to two geographic regions in British Columbia and two in Washington, USA, moving toward the core of the range. Allelic richness and heterozygosity declined substantially as latitude increased. The northernmos2022-01-01T00:00:00Z2022 Mar2025-04-19T09:21:18.771Z2025-04-19T09:21:18.771ZS-EPMC89317713534260410.1002/ece3.8716