History and taxonomy: their roles in the core-satellite hypothesis.

Metapopulation models are important in explaining the distribution and abundance of species through time and space. These models combine population dynamics with stochastic variation in extinction and immigration parameters associated with local populations. One of the predictions of metapopulation models is a bimodal distribution of species frequency of occurrence, a pattern that led to the development of the core-satellite species hypothesis. The spatial scale and taxonomic classification of past core-satellite studies has often been undefined. In our study, we have integrated metapopulation dynamics with the roles that differential dispersal ability and history play in the shaping of communities. The differences in distribution patterns between landbridge islands and oceanic islands, and among various taxa (birds, mammals, herptiles, arthropods, fish, and plants) are analyzed. The majority of landbridge islands comprised locally and regionally abundant species (core species), whereas the majority of oceanic islands had a uniform distribution (or no end-peak in their distribution). The patterns of distribution among the taxonomic groups also showed differences. Birds (good dispersers) consistently showed bimodal- and core-distribution patterns. The bimodal prediction of species distribution is best exemplified in the landbridge islands and in birds, and least in oceanic islands and in organisms other than birds. These results illustrate the importance of testing models with various taxonomic groups and at different spatial scales and defining these scales before formally testing the predictions of the models.