Impact of exotic invasion on the temporal stability of natural annual plant communities

Abstract

Much work in ecology has focused on understanding how changes in community diversity and composition will affect the temporal stability of communities (the degree of fluctuations in community abundance or biomass over time). While theory suggests diversity and dominant species can enhance temporal stability, empirical work has tended to focus on testing the effect of diversity, often using synthetic communities created with high species evenness. We use a complementary approach by studying the temporal stability of natural plant communities invaded by a dominant exotic, Erodium cicutarium. Invasion was associated with a significant decline in community diversity and change in the identity of the dominant species allowing us to evaluate predictions about how these changes might affect temporal stability. Community temporal stability was not correlated with community richness or diversity prior to invasion. Following invasion, community stability was again not correlated with community richness but was negatively correlated with community diversity. Before and after invasion, community stability was positively correlated with the stability of the most dominant species in the community, even though the identity of the dominant species changed from a native (prior to invasion) to an exotic species. Our results demonstrate that invasion by a dominant exotic species may reduce diversity without negatively affecting the temporal stability of natural communities. These findings add support to the idea that dominant species can strongly affect temporal stability, independent of community diversity.