Genetic variation in and from in and around a contact zone.

Climate change poses several challenges to biological communities including changes in the frequency of encounters between closely related congeners as a result of range shifts. When climate change leads to increased hybridization, hybrid dysfunction or genetic swamping may increase extinction risk-particularly in range-restricted species with low vagility. The Peaks of Otter Salamander, , is a fully terrestrial woodland salamander that is restricted to ~18 km of ridgeline in the mountains of southwestern Virginia, and its range is surrounded by the abundant and widespread Eastern Red-backed Salamander, . In order to determine whether these two species are hybridizing and how their range limits may be shifting, we assessed variation at eight microsatellite loci and a 1,008 bp region of in both species at allopatric reference sites and within a contact zone. Our results show that hybridization between and either does not occur or is very rare. However, we find that diversity and differentiation are substantially higher in the mountaintop endemic than in the widespread , despite similar movement ability for the two species as assessed by a homing experiment. Furthermore, estimation of divergence times between reference and contact zone populations via approximate Bayesian computation is consistent with the idea that has expanded into the range of . Given the apparent recent colonization of the contact zone by , future monitoring of range limits should be a priority for the management of populations.