Spatial distribution and competition in two parapatric sibling species of European plethodontid salamanders

The analysis of a zone of parapatric contact between the European plethodon tid salamanders Speleomanyes ambrosii and Speleomantes strinatii in northwe stern Italy (Liguria) has shown that no syntopic populations exist in the a rea. The spatial distributions of both species and their relationships with the main environmental parameters has been investigated at two different s cales. At a larger scale, a vegetation survey has revealed that two main vegetatio n types exist in the contact zone, representing different sets of environme ntal conditions. The two species are distributed according to the observed vegetational-climatic patches, with S. strinatii in the more mesic environm ent and S. ambrosii in the more xeric, and hence less suitable, patches. At a smaller scale, a field experiment artificially created a syntopy, puttin g together specimens of both species in the same micro-environment. This al lowed the study of the spatial distribution of the two species within the e nvironmental micro-patches observed in the caves that Speleomantes use as r etreats. S. ambrosii was again found mainly in the micro-patches that were less effective as refuges, while S. strinatii occupied the patches with ste ady favourable environmental conditions and abundant prey. The comparison o f the two sets of results obtained suggests that the two species compete fo r cover (i.e., a micro-habitat providing high humidity, low temperature and prey availability even during the dry and hot Mediterranean summer). S. st rinatii would be the superior competitor, able to confine S. ambrosii in th e less suitable environment at both scales.