Assessing the roles of patch quality, area, and isolation in predicting metapopulation dynamics

Two aspects of patch geometry-area and isolation-currently dominate the field of metapopulation dynamics. Under this area-and-isolation paradigm, models commonly assume that the probability of local extinction decreases as patch area increases and that the probability of colonization increases as patch connectivity increases. Environmental variables other than patch area and isolation are assumed to have relatively little effect on metapopulation dynamics. Our work on a metapopulation of the butterfly Speyeria nokomis apacheana highlights the need for a broader view of metapopulation dynamics. In this system, neither occupancy nor turnover patterns were best modeled as functions of patch area or isolation. Instead, other measures of habitat quality explained the most variance in occupancy and turnover. Our study also revealed temporal variation in the factors associated with occupancy and turnover. This variation can cause the results of analyses to vary with the temporal scale of analysis. For example, factors associated with turnover in this system differed among single-year and multiple-year analyses. We emphasize that factors other than patch geometry may drive extinction and colonization processes in metapopulations, especially in systems that experience substantial natural and anthropogenic environmental variability.