Rarity in ecology, though often observed, provides a significant challenge to theoretical and empirical ecologists alike. Yenni, Adler, and Ernest (in press) proposed a theoretical mechanism explaining persistent rare species in which the population dynamic causing species to be rare (strong negative density dependence) is also what allows rare species to persist. It remains, however, to determine if ecological communities generally show the theoretical pattern, or if rare species are perhaps controlled by other dominant processes shadowing the effects of strong negative density dependence. The strength of density-dependent population dynamics was estimated using species abundance data from over 60 communities across a broad range of environments and taxonomic groups.
In the majority of cases, rare species showed disproportionately strong negative density dependence. Additionally, a pattern of increasing density-dependence with decreasing relative abundance was seen in most communities, signaling the importance of this dynamic for rare species specifically. Insight into the special population dynamics of rare species will inform conservation efforts in response to climate change and other disturbance.