Fitness landscapes of biotic interactions shape the ecological and evolutionary dynamics of biodiversity

Biotic interactions promote, maintain or reduce diversity within and between species. Ecologists and evolutionary biologists have thus long studied links between biotic interactions and biodiversity dynamics. Yet theoretical and empirical research on these links are still separated by a substantial gap. This gap arises because empiricists rarely quantify the fitness consequences of interactions whereas theoreticians often describe these consequences in a simplistic manner. To bridge this gap, we introduce the concept of ‘fitness landscapes of biotic interactions’ (FLINTs). These landscapes relate the fitness consequence of an interaction for a focal organism to traits of both the focal organism and the interaction partner. FLINTs are an important extension of classical fitness landscape theory since they resolve how biotic environments alter fitness landscapes. We summarize current knowledge about FLINTs and show that their topography can strongly deviate from simplistic trait-matching landscapes implicitly assumed in many theoretical studies. We then illustrate how FLINT topography shapes biodiversity dynamics using an example of co-evolutionary diversification in plants and flower-visiting insects. This leads us to outline a research agenda that measures real-world FLINTs and analyses their consequences for biodiversity dynamics. In summary, FLINTs are a novel framework that fosters integration of theoretical and empirical research on how biotic interactions shape biodiversity dynamics.