The Influence of Seasonality and Stability on the Species Equilibrium

The species equilibrium theory has proven to be a useful framework in which to analyze the distribution and abundance of species, especially for islands and habitats distributed as islands. In this study, the distribution of marine epifaunal invertebrates on rocks has been interpreted using this model. The relationship between area and the number of species present is sustained within this community. However, the increase in the number of species with increasing area appears to result from increasing immigration rather than decreasing extinction, as predicted by the model. Two factors have a major effect on the species equilibrium: seasonality and substrate stability. The seasonality of the climate causes the immigration rate to change seasonally. Colonization curves are dependent on the time of initial immersion of the substrate and vary in shape. However, with time, all converge. A simple model which allows immigration to fluctuate seasonally is developed. It predicts both the initial difference in the ...