The joint role of coevolutionary selection and network structure in shaping trait complementarity in mutualisms

Coevolution can sculpt remarkable trait similarity between mutualistic partners. Yet, it remains unclear which network topologies and selection regimes enhance such trait complementarity. To address this, we simulate coevolution in topologically-distinct net-works under a gradient of mutualistic selection strength. We describe three main insights. First, trait matching is jointly influenced by the strength of mutualistic selection and the structural properties of the network where coevolution is unfolding. Second, the strength of mutualistic selection determines the network descriptors better correlated with higher trait matching. When coevolution is weak, network modularity enhances trait matching, but when it is strong, network connectance amplifies trait matching. Third, the structural properties of networks outrank those of modules or species in determining the evolved degree of trait matching. Our findings suggest networks can both enhance or constrain trait complementary, depending on the strength of mutualistic selection.