Ecological limits to local species richness in Dusky Salamanders (genus Desmognathus)
Camp, Carlos D. | Wooten, Jessica A. | Graham, Sean P. | Pauley, Thomas K.
Species richness commonly varies with elevation, but in many montane regions, the greatest number of species occurs at mid-elevations. A recent regional analysis showed this pattern in Appalachian salamanders of the genus Desmognathus Baird, 1850. The authors proposed that the phylogenetic niche conservatism of these salamanders causes species to accumulate at intermediate elevations, which are characterized by the ancestral climate for the genus. They further suggested that physiological tolerances limit dispersal into higher or lower elevations. We tested this hypothesis using geographic information systems (GIS) based analysis of 235 local Desmognathus communities. Consistent with the regional analysis, local species richness was greatest at mid-elevations. However, the number of species is not limited by physiological tolerances but appears to be restricted ecologically by climate variables favoring aridity, as well as by biotic factors. Whether such ecological limits on species richness at the local level influences richness across regions or evolutionary clades remains to be tested.
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