Distribution of the Bay Checkerspot Butterfly, Euphydryas editha bayensis: Evidence for a Metapopulation Model
This study demonstrates the existence of a metapopulation and infers its approximate spatial extent. Habitat variables and distance from a source of colonists are shown to predict the distribution of local populations. Population sizes are shown to correlate with the area of habitat patches. The spatial pattern of populations, combined with historical information, allows the hypothetical estimation of distance-dependent rates of colonization. A colonization model suggests that "stepping stone" colonization is unimportant. Empirical information on population-size changes is used to estimate yearly extinction probabilities for the small populations with respect to their initial sizes. The metapopulation configurations predicted by a "catastrophic" versus a "continuous" model of extinction are contrasted.