Reproductive Allometry in Three Species of Dusky Salamanders

Desmognathus comprises 21 currently recognized species of salamanders in eastern North America. Assemblages of 3–6 species occur in the Appalachian Mountains, wherein the larger species are more aquatic and the smaller more terrestrial. Adaptive divergence along the habitat gradient from stream to forest involves variation in such life-history traits as age and size at metamorphosis and maturation, survival, propagule size, and fecundity. In this study I examined the tradeoff between egg size and clutch size in North Carolina populations of D. santeetlah, D. ocoee, and D. aeneus, with special emphasis on the latter two species. Traits evaluated included standard length, body mass, trunk volume, egg size, clutch size, and clutch volume. For D. aeneus and D. ocoee, regressions of log-transformed values of body mass and trunk volume on standard length, and trunk volume on body mass, indicated strong similarity between the species in those body proportions that ostensibly constrain female reproductive effort. In all three species bivariate linear regressions of log-transformed values of clutch dimensions on body size suggested little correlation between egg size and body size within species, although larger species had larger eggs, larger clutches, and greater clutch volumes. An apparent interspecific tradeoff between egg size and clutch size in D. aeneus and D. ocoee suggested a common pattern in the relationship between body size and reproductive effort in these species. The results provided further evidence of a high level of life-history invariance in the genus Desmognathus, embodied in tradeoffs, which may stem from morphological conservatism related to specializations of the musculo-skeletal system.