On the role of mutualisms in plant biogeography: consequences for ecology, evolution, and invasion

Most plant species world-wide depend on one or more mutualisms - beneficial associations with other species. Evidence is emerging that these biotic mutualisms shape plant biogeography (i.e. distributions). In particular, the absence of these mutualist partners limits plant establishment (i.e. the mutualist filter). Moreover, this mutualism filter has subsequent consequences for plant ecology, evolution, and invasion. However, a review of such evidence and a synthesis of mechanisms underpinning the mutualist filter are lacking. Therefore, here, I present evidence for the mutualist filter, discuss ecological and evolutionary consequences of this filter, and develop a synthetic framework, generating several cross-mutualist predictions of mutualist filter strength. The mutualist filter should increase with higher mutualist dispersal limitation, specificity and dependency of association, and an increasing number of mutualisms. Together, this offers a path to shift our abiotic and antagonistic centric perspective in plant biogeography to integrate these pervasive mutualistic biotic interactions.