Pace-Of-Life in Dusky Salamanders

In this report I examine tradeoffs involving body size, age, and resource allocation within the framework of the Equal Fitness Paradigm (EFP) in six species of plethodontid salamanders of the genus Desmognathus in two assemblages in the southern Blue Ridge Mountains of North Carolina. The species are representative of the three life-history modes associated with habitat utilization in Desmognathus, namely stream, streamside, and forest. The two assemblages include the largest and smallest members of the genus. Among species, I recorded a negative correlation between body size and relative offspring size, a positive correlation between body size and lifetime offspring number, but negative correlations between body size and both lifetime reproductive investment and productivity, as reflected in the decrease in body size with increasing relative offspring size. In comparing these trends with published data on variation in these parameters in animals generally, I conclude that desmognathan salamanders lie at the slow end of the fast–slow axis in the pace-of-life model of life-history evolution. I discuss possible population regulatory mechanisms that operate on these populations, as a function of life-history mode, with special emphasis on streamside species. I suggest that retention of a brief larval phase in streamside species reflects tradeoffs among dispersal-related traits, including survival and growth.