A general trait-based model for multiplex ecological networks

Ecological networks can represent the structure of food webs, energy flow, and the many and diverse types of interactions between species in ecosystems. Despite its tremendous importance for understanding biodiversity, stability, ecosystem functioning, research on ecological networks has traditionally been restricted to subsets of the species or interactions in ecosystems, i.e., "subnetworks" such as pollination networks or food webs. As a result, the structure of "multiplex" networks that include multiple interaction types is mostly unknown and there is no robust, underlying theory to support their study. Some ecological traits, such as body size or length of mouth parts, are well-known as key predictors of different species interactions. These traits are often strongly related to each other due to evolutionary history, allometry, and selection, and this relatedness may constrain the structure of ecological multiplex networks. We use this idea to develop a model that simulates multiplex ecological networks by interconnecting subnetworks using correlated traits. Our model predicts how multiplex network structure, measured as the overlaps between species functional roles, is affected by neutral processes, interaction rules, and trait constraints, while the structure of individual subnetworks is independent of these trait correlations. Additionally, our model accurately predicts the structure of an observed multiplex network using existing knowledge on species trait correlations and basic features of known ecological subnetworks. This work will stimulate new studies of the structure and dynamics of complex ecosystems by providing a null expectation for how multiplex ecological networks are structured under different ecological conditions.