A novel semantic theory of the assembly rules of interaction networks

Marco A. R. Mello , Sharlene Santana, Pierre-Michel Forget, Cristina Kita, Nastaran Lotfi, Isabel Machado, Renata Muylaert, Francisco Rodrigues, Tanja Maria Straka , Carsten F Dormann

In the web of life, every interaction between species tells a story of cooperation, conflict, or chance. For centuries, ecologists have charted these stories to better understand phenomena such as pollination and disease. We have been using the lens of network science to distill them into topological patterns such as nestedness or modularity. Yet, like in the old buddhist parable of the blind monks and the elephant, these separate views have often missed the bigger picture. In this Perspective, we review the history of topological studies of interaction networks, challenge the “black-and-white” paradigm, and point out a way forward: the Integrative Theory of Interaction Networks (ITIN). This theory unveils the logic of how interaction networks assemble through sequential, rule-bound processes shaped mainly by resource dissimilarity and interaction type. We show that compound topologies are likely the norm in function-oriented, taxonomically-inclusive, well-sampled networks. ITIN is deductive, predictive, and testable, mapping from first principles to real-world systems, thus helping us grasp “the whole elephant”. As ecologists confront the polycrisis, from irreparable biodiversity loss to global health threats, ITIN offers a coherent framework to understand, predict, and restore the threads of the web of life.