Comparing range evolution in two western Plethodon salamanders: glacial refugia, competition, ecological niches, and spatial sorting

Abstract

AbstractAimPlethodon dunni and P. vehiculum are sister species with widely overlapping ranges, yet the distribution of P. vehiculum extends almost 400 km farther north than its sister species. We explore Pleistocene refugial structure, competition, physiological tolerances and dispersal ability as contributing factors to the range difference between these two species.LocationThe Pacific Northwest of North America, including Oregon, Washington and British Columbia – the full range of both species.MethodsWe used genetic, environmental and morphological data to test hypotheses that explain this range difference. Genetic data were used to explore range expansion dynamics and population structure. Species distributional models were used to compare current niches to mid‐Holocene and Pleistocene distributions. Morphological data were used to assess phenotypic differences between the species and test for evidence of spatial sorting.ResultsBoth species underwent rapid range expansions since the Pleistocene and share similar population structure. Species distributional models are different in distribution at all times periods between species. The species are significantly different in all morphological measurements taken. Only P. vehiculum shows evidence of spatial sorting.Main conclusionsPhysiological tolerance and dispersal ability best explain the distributional difference between these species. Spatial sorting most likely plays a key role in the range expansion of P. vehiculum.