The stability of forest biodiversity

The neutral model says that the relative abundance of a species is as likely to increase as it is to decrease, because species are ecologically identical1. This hypothesis can be rejected if variance does not increase over time2. We used a more powerful test, based on comparisons among locations, to show that variability stabilizes and, for most species, decreases over thousands of years3. The neutral model also predicts that after a perturbation, relative abundance is as likely to increase as it is to decrease.