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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.235.251.160 on Mon, Abstract. In the southern Appalachians three congeneric salamanders-Desmognathus quadramaculatus, D. monticola, and D. ochrophaeus-are broadly sympatric. D. monticola is intermediate to the other species in body size and in degree of terrestrial habit. This study analyzed the roles of competition, predation, and habitat conditions in limiting the abundance of this "ecologically intermediate" species and in directing its evolution. In field observations, D. monticola regularly used both stream-bank and forest-floor habitats; experimental exclusion from either of these habitats resulted in poor survival. Field enclosure experiments also showed that growth, survival, and habitat selection of D. monticola were altered by the presence of congeners. Interference from conspecifics and from congeners of equal size decreased growth and reduced survival of D. monticola. Predation by large D. quadramaculatus sharply reduced survival of juveniles and caused shifts in activity and habitat selection. I suggest that predation has controlled the evolution of body size and habitat selection in D. monticola and that populations of this intermediate species are limited by the availability of streambank cover as a refuge from predation. Competition may also be important among species of similar size when food is limited.

Four sympatric species: Desmognathus quadramaculatus, D. monticola, D. fuscus, and D. ochrophaeus, showed different substrate preferences in experimental trials. In addition, the choices of substrates and of cover objects were influenced by the presence of other salamanders. Significant differences in substrate choice were found for each pair of species. The ratio of rocky to woody substrate chosen was lower for the more terrestrial species. The ecologically intermediate species, D. monticola, exhibited the broadest choice of substrate and shifted its choice when confined with congeners. Adults of D. monticola became more active and avoided the preferred substrate of D. quadramaculatus when confined with that species. Juveniles of D. monticola became less active but also avoided preferred substrates of the larger D. quadramaculatus. In 1-m 2 arenas with four cover objects, small individuals of the three more terrestrial species avoided cover occupied by large individuals of these species. No aggressive behavior patterns were observed in 100 encounters of different individuals. These results suggest that this assemblage of salamanders is structured by species-specific microenvironmental preferences that are affected by interspecific interactions. Avoidance of other salamanders is the common response that segregates individuals and species. This avoidance is likely an adaptation to the severe risk of predation faced by small salamanders.