SYNTOPIC COEXISTENCE AND HABITAT USAGE IN TWO MORPHOLOGICALLY SIMILAR PLETHODON SPECIES

Abstract

Numerous studies have shown terrestrial salamanders of similar size compete strongly for cover objects on the forest floor. The cover objects provide a refuge that allows the owner more foraging opportunities throughout the year. Usually the competition between species is asymmetric and results in the exclusion of one of the species from large areas. In Hoosier National Forest, Plethodon cinereus and P. dorsalis coexist broadly and appear to share the same microhabitats. A number of factors might explain this unique case of coexistence. P. cinereus is more common in drier habitats and becomes more predominant as spring becomes warmer and drier compared to P. dorsalis. P. dorsalis is more common in the moister habitats, and predominates early in the spring. P. cinereus also looses water more slowly compared to P. dorsalis. Although P. cinereus is larger and shows higher levels of aggressive behaviors associated with cover object defense, P. dorsalis is better able to hold ownership of cover objects in the lab. The coexistence may be the result of the greater physiological tolerance of P. cinereus to drier conditions, which allow it to feed in habitats and at times unavailable to P. dorsalis. As conditions on the forest floor get warmer and drier as spring progresses, the more sensitive P. dorsalis has to retreat underground sooner than P. cinereus. P. cinereus will then have foraging opportunities under cover objects that are unavailable to P. doralis due to its sensitivity.