Searching for Stability

Understanding how multiple competing species can inhabit the same natural communities has been one of the most enduring challenges of ecology. Barring specific stabilizing mechanisms, diversity should erode over time as fitness differences lead to rapid competitive exclusion, although species with similar fitness might co-occur for longer periods during a random walk to extinction. Empirical studies addressing coexistence have lagged theoretical work, and this dissertation aims to address this knowledge gap. I focus on predation and some of the ways in which predation may contribute to stability, moving from laboratory microcosms to field enclosures, and from temporary ponds to the rocky intertidal. In chapter one, I show that larval salamanders tend to consume the most frequent prey in microcosms, consistent with frequency-dependent predation being a stabilizing force. However, some prey are always highly preferred, and would experience no refuge in rarity. In chapter two, I find that the overall effect of salamander predation on a zooplankton assemblage is to decrease diversity in pond enclosures, possibly due to small plankton population sizes in the enclosures. And in chapter three, I show that the rocky intertidal community can be quite robust to perturbation, with the predominant members each able to reinvade following experimental removals in the field, whereas the effects of predator exclusion on regrowth are minimal. Here, the provisioning of space through disturbance and the subsequent dynamics of recolonization are the likely drivers of coexistence. The evidence I accumulate shows that predation can have a strong influence on some communities, but it is not a singular and general driver of stable coexistence in multispecies communities