Neutral Theory Overestimates Extinction Times in Nonhuman Primates

The unified neutral theory of biodiversity states that random processes and stochastic events drive species abundance and turnover and that each lineage has an equal probability of speciation. Predictions based on this model have been tested only a few times using evolutionary rates. We used an individual-based approach to estimate the waiting times to extinction (the time between one extinction event and the next) and compare those with the neutral model. We calculated the speciation and extinction rates for all subfamilies in the primate order using a time-calibrated phylogeny and compared the estimates against those predicted by the neutral theory using taxon area distribution and population densities. In most cases, the extinction time obtained from the neutral theory exceeded that estimated using phylogenetic data by several orders of magnitude. Our main result indicates that drift is too slow to fully explain evolutionary rates of turnover in primates, suggesting that other factors besides chance may influence primate diversification rates. Although estimates of forest cover, taxon area distribution, and species densities may influence the results, the observed differences do not support the predictions of neutral theory and question the model as a reference for conservation purposes.