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SPATIALLY AUTOCORRELATED DEMOGRAPHY AND INTERPOND MIGRATION IN THE CALIFORNIA TIGER SALAMANDER (AMBYSTOME CALIFORNIENSE)
Trenham, P. C., W. D. Koenig, AND H. B. Shaffer. SPATIALLY AUTOCORRELATED DEMOGRAPHY AND INTERPOND MIGRATION IN THE CALIFORNIA TIGER SALAMANDER (AMBYSTOME CALIFORNIENSE). ECOLOGY 82:3519-3530, (2001).
We investigated the metapopulation structure of the California tiger salamander (Ambystoma californiense) using a combination of indirect and direct methods to evaluate two key requirements of modern metapopulation models: 1) that patches support somewhat independent populations linked by migration; and 2) that interpatch migration rates decline as distance increases. Over 3 consecutive field seasons we marked, measured, and released more than 1300 adult California tiger salamanders at 10 breeding ponds separated by 60 to 3000 m. Our analysis of spatial autocorrelation of pond demography suggest that ponds support somewhat independent populations and that migration rates between ponds is inversely related to distance. Direct observations of interpond movement by marked individuals confirmed the conclusions of the autocorrelation analyses, but also suggest that factors other than distance may also impact rates and patterns of interpond movement. While this system fits a broadly defined metapopulation structure, the presence of highly unequal subpopulation sizes combined with a few potentially interacting patches suggests that regional persistence will depend more upon the local dynamics of the largest subpopulation(s) than a classical metapopulation balance between local extinction and colonization.