Mathematical Biology Seminar Peter Adler Department of Forest, Range, and Wildlife Sciences Utah State University Wednesday, Feb 15, 2006 "Does climate variability stabilize plant species coexistence? A test of current theory with really old data" Abstract: Theoretical ecologists often complain that empiricists ignore their work, and instead run around measuring all the wrong things. This seminar provides a rare opportunity to see what actually happens when a field ecologist with poor math skills makes a determined attempt to test theory. The theory in question involves the "storage effect," which describes how temporal environmental fluctiations can stabilize the coexistence of competing species. This coexistence mechanism is relevant to questions about how climate change will impact species diversity, since climate variability is forecast to increase in the future. I test the theory by analyzing a unique demographic dataset collected in Kansas prairie from 1937-1972 with a hierarchical Bayesian model. The results show that i) the dynamics the three perennial grass species satisfy all requirements of storage effect theory, ii) climate variables are correlated with interannual variation in performance of these three species, and iii) temporal variability increases low density growth rates, buffering these species against competitive exclusion. I discuss implications of these results for recent neutral theories of diversity, and also for predicting the effects of global change on species diversity.