Abundance determines core–periphery roles of birds in a Neotropical seed dispersal network

Abstract

Frugivorous birds assume different roles in the organization of seed dispersal networks depending on how they interact with plants. Identifying the birds with the most important structural roles can shed light on how seed dispersal systems function. Here, we characterized the seed dispersal network in a megadiverse Neotropical bird community from Brazil and quantitatively scored birds according to their importance in the network. We tested the applicability of the recent core–periphery framework based on stochastic block models and contrasted it with other metrics commonly used in ecological networks to define structurally important species. Then, we also evaluated the main attributes (body mass, degree of frugivory and abundance) associated with the role of frugivorous birds in the network. In the field we recorded 1132 mutualistic interactions between 44 bird species and 41 plant species. We identified the Silver‐beaked Tanager Ramphocelus carbo, Band‐tailed Manakin Pipra fasciicauda and Red‐legged Honeycreeper Cyanerpes cyaneus as the most important seed‐dispersers. Our study highlighted the utility of the core–periphery method in identifying relevant species in the context of networks, which gave slightly different results to other approaches. Specifically, the core–periphery assessment identified more species as relevant, including the large frugivore Bare‐faced Curassow Crax fasciolata. Finally, we discovered that bird abundance was the main predictor of a species' role. We conclude that abundant and generalist frugivorous birds are key components in the maintenance of ecosystem function in the studied ecosystem.