Interspecific aggression and spatial relationships in the salamanders Plethodon kentucki and the Plethodon glutinosus: Evidence of interspecific interference competition

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Competitive interactions among widely sympatric species of terrestrial plethodontid salamanders have received little attention, I investigated whether interspecific interference competition for space occurs between one such pain of species, Plethodon kentucki and P. glutinosus. Encounters between heterospecific adults in the laboratory resulted in aggressive interactions as often as did encounters between conspecific adults. However, intense aggression (bite-holds) occurred more often during pairings between conspecifics, indicating that interference competition is greater among individuals of the same species. Plethodon glutinosus was dominant more often than P. kentucki during encounters with heterospecifics in the laboratory. During a second laboratory experiment, both species preferentially used large cover sites in single-species control groups, whereas P. kentucki used small cover sites significantly more often in mixed-species experimental groups, indicating competitive exclusion of P. kentucki by the larger P. glutinosus. In natural habitats, individuals of both species were usually found alone under cover objects, and the extent of home-range overlap did not differ between conspecifics and heterospecifics. My results indicate that these species compete for space and defend territories against heterospecifics as well as conspecifics. Greater intraspecific than interspecific interference competition may permit coexistence if the former is more important in limiting the population growth of each species.

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Canadian Journal of Zoology

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