9520600 Singer Metapopulations are collections of populations that interact through dispersal. Their persistence in the face of population extinctions relies on colonization; the establishment of new populations in unused habitat. However, mechanistic studies of colonization in natural systems are lacking, even though mechanism at this scale may strongly structure large-scale metapopulation dynamics. The goal of this research is to investigate the behavioral and ecological mechanisms that structure colonization in a metapopulation of the checkerspot butterfly. The metapopulation, located in the Sierra Nevada of California, recently suffered a set of weather-induced population extinctions, and provides unoccupied habitat patches for study. Behavioral mechanisms to be studied include habitat preference and host-plant search efficiency within habitats. The ecological mechanisms are temporal and spatial patterns in habitat quality and host-parasitoid relations between the checkerspot butterfly and a braconid wasp. Preliminary results indicate that colonization is occurring slowly, that habitat quality is highly structured temporally, and that habitat preference is not optimal, but depends instead on history of host use at the study site. This study will contribute significantly to basic understanding of the role of dispersal in maintaining metapopulation structure, and some of the mechanisms governing colonization of new habitat patches. The results will have broad application to resource management strategies and attempts to conserve biodiversity.
