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DEMOGRAPHY AND SPATIAL POPULATION STRUCTURE IN CALIFORNIA TIGER SALAMANDER
Citation:
Trenham, P. C. DEMOGRAPHY AND SPATIAL POPULATION STRUCTURE IN CALIFORNIA TIGER SALAMANDER. Presented at Biology Department, Gustavus Adolphus College, Saint Peter, MN, May 2, 2000.
Description:
Although the causes of many amphibian declines remain mysterious, there is general agreement that human habitat alteration represents the greatest threat to amphibian populations. In January 2000 the US Fish and Wildlife Service proposed listing Santa Barbara County California Tiger Salamanders (Ambystoma californiense) as endangered due to habitat loss. We have been studying the demography, terrestrial habitat use, and interpond movements in a population of California tiger salamanders in Monterey County. At our long-term study pond we have marked all breeding adults and newly metamorphosed juveniles since January 1991. Over this period the production of juveniles has been insufficient to maintain a viable population, suggesting that immigrants from other ponds may support this population. Radiotracking indicated that most adults move less than 200 m from the pond during post-breeding emigration, spending the summer in the burrows of ground squirrels and gophers. To assess the rate and spatial extent of interpond movement, from 1996-1998 I captured, marked, and released 1216 breeding adults at nine additional ponds. Approximately 20% of breeding males and females were recaptured at ponds other than those where they had been marked. Dispersers moved between ponds separated by 50-670 m, and we estimate maximum dispersal capacity to be 1 km. These observations suggest that, in the absence of barriers, a regular stream of dispersers will maintain breeding populations at ponds isolated by less than 1 km from productive sites. Additionally, from a population genetics perspective, only ponds isolated by more than 1 km would be expected to exhibit significant divergence.