Life-history perspective of adaptive radiation in desmognathine salamanders

This study investigates interspecific variation in age at first reproduction, fecundity, and body size in multispecies assemblages of desmognathine salamanders. The hypotheses tested are that interspecific differences in body size among desmognathines stem proximately from variation in age at first reproduction and that variation in the latter trait is positively correlated with variation in fecundity among species. It is shown that a correlation between age at first reproduction and fecundity, combined with a uniform rate of survival, based on available estimates of these parameters, will yield equivalent values of net reproductive rate (R(o)) among the species of a given assemblage. Such equivalence represents a form of life-history symmetry. Data from two assemblages are presented in support of the argument for symmetry. Such life-history symmetry may reflect uniformity in morphological specialization in desmognathines. Given the morphological adaptations to burrowing (head-wedging) in the subfamily, the relationship between adult body size and habitat preference in Desmognathus may reflect adaptation to the size of cover objects and composition of the substratum along the aquatic-terrestrial habitat gradient, I propose that these variables, in association with predation and competition, represent the selective factors responsible for body size diversification in Desmognathus.