Trait-mediated interaction leads to structural emergence in mutualistic networks
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As asymmetric structures of mutualistic networks can potentially contribute to system resilience, elucidating drivers behind the emergence of particular network architectures remains a major endeavour in ecology. Here, using an eco-evolutionary model for bipartite mutualistic networks with trait-mediated interactions, we explore how particular levels of connectance, nestedness and modularity are affected by three network assembly forces: resource accessibility, tolerance to trait difference between mutualistic pairs and competition intensity. We found that a moderate accessibility to intra-trophic resources and cross-trophic mutualistic support can result in a highly nested web, while low tolerance to trait difference between interacting pairs leads to a high level of modularity. Network-level trait complementarity leads to low connectance and high modularity, while network-level specialization can result in nested structures. Consequently, we argue that the interplay of ecological and evolutionary processes through trait-mediated interactions can explain these widely observed architectures in mutualistic networks.
KeywordsNetwork architecture Nestedness Connectance Compartmentalization Modularity Trait complementarity Network specialization
We are grateful to Ulf Dieckmann, Åke Brännström, Feng Zhang, Pietro Landi for constructive comments, and to Beverley Laniewski for English editing. CH is a South African Research Chair in Mathematical and Theoretical Physical Biosciences, funded by the South African National Research Foundation (Nos. 76912 and 89967); HOM receives a PhD Scholarship from the Deutscher Akademischer Austausch Dienst (DAAD; German Academic Exchange Service). The project is also partially supported by the Australian Research Council (Discovery Project DP150103017).
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