Understanding the forces shaping ecological communities is crucially important to basic science and conservation. In recent years, considerable progress was made in explaining communities using simple and general models, with neutral theory as a prominent example. However, while successful in explaining static patterns such as species abundance distributions, the neutral theory was criticized for making unrealistic predictions of fundamental dynamic patterns. In particular, the theory predicts unrealistically long times to extinction of species, and too small population fluctuations. Moreover, the predictions of the theory are extremely sensitive to the assumption that all species have equal fitness. We tested whether incorporating environmental fluctuations into the neutral framework (i.e. species have fluctuating fitness, but are equivalent on the long run) could resolve these limitations.
Results/Conclusions
Applying the theory to real data (the tropical forest of Barro Colorado Island), we found that it better fits the observed distribution of short-term fluctuations, the temporal scaling of such fluctuations, and the decay of compositional similarity with time, than the original theory, while retaining its power to explain static patterns of species abundance. Moreover, the predictions are robust to mild fitness differences due to the emergence of the storage effect, and the time to extinction of abundant species is much shorter than in the original theory. Importantly, although the proposed theory is neutral (all species are equivalent) and stochastic, it is a niche-based theory in the sense that species differ in their demographic responses to environmental variation. Our results show that this integration of niche forces and stochasticity within a minimalistic neutral framework is highly successful in explaining fundamental static and dynamic characteristics of ecological communities.