Douglas Erwin, Thomas Olszewski

Paper #: 03-12-067

Understanding the response of ecological communities to environmental change is critical to forecasting the possible consequences of modern global change. The fossil record preserves the results of numerous natural experiments in ecological change, but evaluating the dynamics of ancient communities is difficult because it is not possible to directly observe interactions among extinct organisms. Dynamic and neutral models of communities1-4, however, reveal the signature of processes like migration, competition, recruitment, and extinction in species abundance distributions, which can be well preserved in the rock record5,6. Here we show that brachiopod abundance distributions from four temporally distinct ecological landscapes from the Permian of the Glass Mountains (Texas) show significant differences in their maximum likelihood neutral model parameters. In addition, the abundance distributions of these communities are better fit by the neutral zero-sum multinomial distribution than by the classical lognormal distribution7. The observed patterns suggest that ecological communities can accommodate changes in environment, associated with second order fluctuations in sea level in this case, through adjustments in rates of species production and immigration while remaining diverse in terms of taxonomic and functional composition.