Abstract: While evidence for the stabilizing effects of species diversity on ecosystem functions and properties has been accumulating, the roles of some basic ecological processes, such as interspecific competition, in regulating ecosystem temporal stability remain poorly understood. Modern coexistence theory has recognized the importance of species niche differences and relative fitness differences for determining competitive outcomes. However, the linkage between these factors and ecosystem temporal stability has yet to be explored. In this study, using laboratory microcosms containing assemblages of freshwater bacterivorous protists as a model system, we show that interspecific competition promoted species asynchrony, but did not alter population temporal stability. Moreover, we found that species niche differences increased species asynchrony, whereas species fitness differences decreased population stability, resulting in changes in the temporal stability of total community abundance. Our findings provide rare experimental evidence that mechanisms regulating species coexistence influence ecosystem stability, facilitating a more mechanistic understanding of the role of interspecific competition for ecosystem stability.
