PARENT SESSION
Oral Session # 27: Wetland Ecology II: Amphibians, Chemical Cycling, and Tidal Forests.
Presiding: D Jenkins
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 101.

Risk of reproductive failure and persistence of the Marbled Salamander (Ambystoma opacum) in a wetland pond.

Taylor, Barbara^*,1, Scott, David¹, Gibbons, J.¹, ¹ Savannah River Ecology Laboratory, Aiken, SC

ABSTRACT- For amphibians that breed in wetland ponds, disturbance may often be the most important factor affecting reproductive success. We analyzed a 24-yr record of breeding adults and juvenile recruits for the marbled salamander, Ambystoma opacum, at Rainbow Bay, a seasonal wetland pond on the Savannah River Site in South Carolina. Complete reproductive failure occurred in 6 of 22 yr when the species bred and near complete failure in an additional 4 yr. These failures were due mainly to late filling or early drying of the pond. A computer simulation model for population dynamics of A. opacum, developed previously for this species on the SRS, enabled us to infer levels of survival in pond and upland habitat necessary to produce the observed levels of recruitment and to maintain breeding populations. We then used the model to explore persistence of the populations when catastrophic mortality is applied to aquatic stages. The model is age-structured. It tracks terrestrial females individually, so that effects of demographic stochasticity on breeding and death are represented. Catastrophic reproductive failure has a profound effect on population dynamics, and the probability of extinction is consequently fairly high for plausible values of survival in the upland habitat. Details of life history, particularly life span, become important to predicting persistence. The high probability of reproductive failure makes the population extremely susceptible to local extinction, but the high reproductive capacity also renders it amenable to rescue by recolonization. These results underscore the importance of understanding and managing dynamics of this species at the meta-population level.

Key words: reproductive success, wetland ponds, amphibian population dynamics, disturbance