Morphological convergence and coexistence in three sympatric North American species of Microtus (Rodentia: Arvicolinae)

Niche theory predicts that ecologically identical species cannot stably coexist in local communities. My aim was to investigate morphological diversity as a possible factor enabling the coexistence of a species-rich Microtus (Rodentia: Arvicolinae) fauna in a hotspot of North American mammalian diversity, the Greater Yellowstone Ecosystem (GYE). LOCATION: The Greater Yellowstone Ecosystem, North America. METHODS: Using in-hand morphological measurements of size and shape, I compared the morphologies of three North American vole species (Microtus spp.), in sympatry in the GYE and in allopatry across their ranges, in order to examine: (1) whether morphologies are fixed or plastic and (2) the degree of morphological character displacement or convergence in sympatric species. RESULTS: Support was found for plasticity of morphology for all three vole species: M. longicaudus, M. montanus and M. pennsylvanicus. However, Microtus individuals of all species from the GYE area of sympatry were mo...