Plant interaction networks reveal the limits of our understanding of diversity maintenance

Species interactions are key drivers of biodiversity and ecosystem stability. Current theoretical frameworks for understanding the role of interactions make many assumptions which unfortunately, do not always hold in natural, diverse communities. This mismatch extends to annual plants, a common model system for studying coexistence, where interactions are typically averaged across environmental conditions and transitive competitive hierarchies are assumed to dominate. We quantify interaction networks for a community of annual wildflowers in Western Australia across a natural shade gradient at local scales. Whilst competition dominated, intraspecific and interspecific facilitation were widespread in all shade categories. Interaction strengths and directions varied substantially despite close spatial proximity and similar levels of local species richness, with most species interacting in different ways under different environmental conditions. Contrary to expectations, all networks were predominantly intransitive. These findings encourage us to rethink how we conceive of and categorize the mechanisms driving biodiversity in plant systems. Current theories for understanding and predicting the maintenance of diversity in plant systems focus almost exclusively on competition. We describe plant–plant interaction networks in a diverse, empirical wildflower community co‐occurring under a range of environmental conditions. Intraspecific and interspecific facilitation were widespread and networks were predominantly intransitive, suggesting that the processes maintaining diversity in this system are not operating according to competition‐based expectations and highlighting the need for alternative frameworks of diversity maintenance.