Life Histories and Comparative Demography of Two Salamander Populations

Publisher Website
Google Scholar
Abstract
Two populations of the plethodontid salamander D. ochrophaeus inhabiting wet, vertical rockfaces in the southern Appalachian Mountains were censused by the Jolly-Seber multiple recapture method over 7 yr. The populations were known to differ in age at sexual maturity, and a primary goal of the study was to obtain survivorship estimates that would permit comparisons of overall life histories of the 2 populations. Low elevation juveniles grow faster than high elevation juveniles during fall, winter and spring of their 1st full year. They grow more slowly than equal-aged high elevation animals and become externally sexable in their 3rd summer, a year earlier than juveniles of the high elevation population. During the summer high elevation individuals of all sizes grow faster than those of corresponding size and sex in the low elevation population, since growth rates decline with attainment of sexual maturity. Estimated densities were about 3 sexable males and 3 sexable females/m2 for both populations throughout the study. The co-occurrence of a potential predator and competitor, D. monticola, at the low elevation site had no discernible effect on density of D. ochrophaeus. Survivorship of sexable animals appears to be higher over the colder months at the high elevation site; survivorship from June to Aug. appears similar for the 2 populations. Annual survival rates were estimated to be 0.743 and 0.626 for high and low elevation animals that are externally sexable. Recruitment appears to balance losses in both populations. Estimated probabilities of survival from hatching to 1st oviposition were 0.059 and 0.087 at the high and low elevation sites. The difference reflects age differences at maturity. Fertility rates appear to be uncorrelated with age in both populations, but larger females lay more eggs so that clutch sizes are higher in the high elevation population. Life tables employing the estimates of survivorship to 1st reproduction, annual adult survivorship, and age-specific fertility R0 values of approximately unity, indicating that the approximations of life history parameters are reasonably good. The life history and demographic differences between high and low elevation D. ochrophaeus populations might reflect evolutionary divergence and adaptation, the direct effect of environment on maturation and growth rates, or some combination of the 2.

This publication has 4 references indexed in Scilit: