Ecological parapatry and competition in two sibling species of European plethodontid salamanders.

The analysis of a zone of parapatric contact between the European plethodontid salamanders Speleomantes ambrosii and Speleomantes strinatii in northwestern Italy (Liguria) has shown that no syntopic populations exist in the area. The spatial distributions of both species and their relationships with the main environmental parameters has been investigated at two different scales. At a larger scale, a vegetation survey has revealed that two main vegetation types exist in the contact zone, representing different sets of environmental conditions. The two species are distributed according to the observed vegetationalclimatic patches, with S. strinatii in the more mesic environment and S. ambrosii in the more xeric, and hence less suitable, patches. At a smaller scale, a field experiment artificially created a syntopy, putting together specimens of both species in the same micro-environment. This allowed the study of the spatial distribution of the two species within the environmental micro-patches observed in the caves that Speleomantes use as retreats. S. ambrosii was again found mainly in the micro-patches that were less effective as refuges, while S. strinatii occupied the patches with steady favourable environmental conditions and abundant prey. The comparison of the two sets of results obtained suggests that the two species compete for cover (i.e., a micro-habitat providing high humidity, low temperature and prey availability even during the dry and hot Mediterranean summer). S. strinatii would be the superior competitor, able to confine S. ambrosii in the less suitable environment at both scales.