Biogeographic kinetics: estimation of relaxation times for avifaunas of southwest pacific islands

Abstract

When species diversity S on an island is displaced from the equilibrium value by injection or removal of species, S relaxes to equilibrium by an imbalance between immigration and extinction rates. Estimates of exponential relaxation times, t(r), for avifaunas of New Guinea satellite islands are calculated from analysis of four "experiments of nature": recolonization of exploded volcanoes, contraction in island area due to rising sea level, severing of land bridges, and disappearance of landbridge relict species. t(r) is in the range 3,000-18,000 years for avifaunas of islands of 50-3000 square miles (130-7800 km(2)), and increases with island area. Immigration coefficients decrease and extinction coefficients increase with increasing S. The results may be relevant to the design of rainforest preserves.