The effect of mutualistic interactions on diversity patterns in island biogeography

Islands are often regarded as “natural laboratories” for biology, and this applies also to ecological interactions between species that co-occur on islands. Mutualistic interactions, the association between organisms of two different species in which each benefits, should have important effects on the ability of species to establish, speciate or persist on islands. However, while island biogeography models increasingly incorporate the dynamics of biotic interactions in island ecosystems, current approaches do not consider the complexities introduced by mutualistic relationships, e.g., mutualism-driven immigration, cospeciation between mutualistic partners, dynamic formation and loss of mutualistic links. Here we present a new simulation model of island biogeography that explicitly includes mutualistic interactions and their influence on biodiversity at macroevolutionary scales. With this approach, we aim to better understand the effect of mutualism on insular diversity patterns over macroevolutionary time. Our model shows how mutualism influences species immigration, diversification and persistence through its effects on species-level processes. Strong mutualism is associated with higher species richness and more connected communities, while networks with weak or absent mutualism remain fragmented, with many species failing to establish interactions. By extending classical island biogeography to include ecological interaction networks, our study offers a new theoretical lens on how mutualism can influence biodiversity patterns and network structures in insular systems over evolutionary timescales.