Mechanisms of successional dynamics: Consumers and the rise and fall of species dominance

Insight into potential mechanisms of succession following disturbance to an ecological community can be gained by considering processes that contribute to the rise (colonization, interactions with established species) and demise (differential mortality) of specific stages within the successional sequence. Most successional theories focus on the rise to dominance, assuming demise is the result of competition, but other factors can cause differential mortality among species, including physical disturbance, senescence, and consumers. In rocky intertidal communities on the coast of Washington state, USA, gaps in mussel beds exhibit a succession from predator‐susceptible to predator‐resistant species following disturbance, suggesting that differential consumption by mobile species may play an important role in the demise of early succession species and the eventual dominance of the mussel Mytilus californianus . Experimental manipulation of a dominant species earlier in succession, the blue mussel Mytilus trossulus , demonstrated that this species inhibits the invasion of M. californianus in the absence of predators. Experimental manipulation of predatory snails ( Nucella emarginata and Nucella canaliculata ), which feed heavily on M. trossulus but not M. californianus , greatly increased the rate at which M. californianus invaded gaps. These results and those of other studies indicate that consumers frequently have important effects on the dynamics of succession in benthic marine systems, and might also play a role in other settings.