Mechanisms of invasions: can the recipient community influence invasion rates?

At least since Elton's work in the 1950s it has been argued that properties of recipient communities influence invasion rates. The widespread view, initiated by Elton and later supported by both empirical and modelling studies, is that species-rich communities are more resistant to invasion than species-poor communities in otherwise identical habitats. However, the dynamics of some empirical systems do not support this idea, but reveal instead a positive relationship between species richness and invasion, reflecting the particular attributes of component species and their interactions. These findings cannot be explained solely by Shea and Chesson's (2002) attempt to reconcile divergent observations of both positive and negative relationships between invasion rates and richness of the recipient community. Here, based on the behaviours of several models, we develop an alternative view that invasion success is related positively to variability in resource availability. This variability can arise in many ways, dependent in part on the life history features of component species, the nature of interactions among species, and the spatial arrangement of individuals on a landscape. Our overall conclusion is that the ability of a community to resist the establishment of new populations comes not from species richness, diversity or the average connectivity of the system per se, but from the ability of established species to utilise the maximum amount of resources in the long term and realise the smallest amount of variability in resource availability. We argue that seaweed communities adhere to this principle