Comparison of Two Types of Metapopulation Models in Real and Artificial Landscapes

Application of metapopulation models is becoming increasingly widespread in the conservation of species in fragmented landscapes. We provide one of the first detailed comparisons of two of the most com- mon modeling techniques, incidence function models and stage-based matrix models, and test their accuracy in predicting patch occupancy for a real metapopulation. We measured patch occupancies and demographic rates for regional populations of the Florida scrub lizard ( Sceloporus woodi ) and compared the observed oc- cupancies with those predicted by each model. Both modeling strategies predicted patch occupancies with good accuracy (77-80%) and gave similar results when we compared hypothetical management scenarios involving removal of key habitat patches and degradation of habitat quality. To compare the two modeling approaches over a broader set of conditions, we simulated metapopulation dynamics for 150 artificial land- scapes composed of equal-sized patches (2-1024 ha) spaced at equal distances (50-750 m). Differences in predicted patch occupancy were small to moderate ( � 20%) for about 74% of all simulations, but 22% of the landscapes had differences of � 50%. Incidence function models and stage-based matrix models differ in their approaches, assumptions, and requirements for empirical data, and our findings provide evidence that the two models can produce different results. We encourage researchers to use both techniques and further exam- ine potential differences in model output. The feasibility of obtaining data for population modeling varies widely among species and limits the modeling approaches appropriate for each species. Understanding differ- ent modeling approaches will become increasingly important as conservation programs undertake the chal- lenge of managing for multiple species in a landscape context.