American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Partner fidelity and asymmetric specialization in ecological networks”

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Miguel A. Fortuna, Arxhina Nagavci, Matthew A. Barbour, and Jordi Bascompte (Sep 2020)

Asymmetric specialization leaves a pervasive signature on the biogeography of mutualistic interactions

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Abstract

Species are embedded in complex networks of interdependencies that may change across geographic locations. Yet, most approaches to investigate the architecture of this entangled web of life have considered exclusively local communities. In order to quantify to what extent species interactions change at a biogeographic scale, we need to shed light on how among-community variation affects the occurrence of species interactions. Here, we quantify the probability for two partners to interact wherever they co-occur (i.e., partner fidelity) by analyzing the most extensive database on species interaction networks worldwide. We found that mutualistic species show more fidelity in their interactions than antagonistic ones when there is asymmetric specialization (i.e., when specialist species interact with generalist partners). Moreover, resources (e.g., plants in plant-pollinator mutualisms or hosts in host-parasite interactions) show a higher partner fidelity in mutualistic than in antagonistic interactions, which can be explained neither by sampling effort, nor by phylogenetic constraints developed during their evolutionary histories. In spite of the general belief that mutualistic interactions among free-living species are labile, asymmetric specialization is very much conserved across large geographic areas.