Most existing experimental and theoretical studies suggest that diversity is an effective barrier to plant invasion. However, these studies may be limited in their generality, because they involve relatively small numbers of species or examine only short time periods. To evaluate how invasions are controlled in more realistic situations, Meiners, Cadenasso, and Pickett analysed data from 42 continuous years of sampling old field succession.
In contrast to the experimental literature, they found that when richness was related to invasion dynamics, it enhanced rather than impeded invasion. A mixture of factors, including resident species composition, total community cover, and species richness, determined invasion control. This research, published in the upcoming issue of Ecology Letters, calls into question the ubiquity of diversity as an ecological barrier to invasion, and suggests that each invasion has its own, unique suite of factors that constrain success.
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