FECUNDITY IN PRIMITIVE PLETHODONTID SALAMANDERS

The Plethodontidae, with 23 genera and over 180 species, has more living members than any other family of salamanders. The geographic distribution of the group includes most of the forested region of temperate North America, the American tropics, and a restricted area of southern Europe. Wilder and Dunn (1920) believed that plethodontids originated in Appalachia as a group adapted to life in mountain streams, and that the subsequent radiation from Appalachia was facilitated by adaptation to more terrestrial modes of life. Dunn (1926) and Wake (1966) elaborated on this hypothesis, and both authors considered Gyrinophilus and Pseudatriton to be the most primitive existing members of the family. The species of Gyrinophilus, including G. porphyriticus and a paedogenetic derivative, G. palleucus, are highly aquatic salamanders occupying springs, small streams, and cave waters of the Appalachian region. Pseudotriton is also represented by two, species, P. ruber and P. montanus, both of which are more terrestrial than Gyrinolphilus (Bruce, 1968, and unpublished data). Pseudotriton ruber occurs in both upland and lowland habitats throughout a large area of the eastern United States, whereas P. montanus occupies lowland habitats in the Southeast. If the mountain streams of Appalachia represent the ancestral adaptive zone of plethodontids, then Pseudotriton shows advances over Gyrinophilus in geographic distribution and habitat associations. A comparison of the life cycles of the species of Gyrinopiilus and Pseudotriton might indicate trends in the early evolution of plethodontid life history features. In