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Dryad

Individual-based networks reveal the highly skewed interactions of a frugivore mutualist with individual plants in a diverse community

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Aug 27, 2021 version files 267.23 KB

Abstract

While plant-animal interactions occur fundamentally at the individual level, the bulk of research examining the mechanisms that drive interaction patterns has focused on the species or population level. In seed-dispersal mutualisms between frugivores and plants, little is known about the role of space and individual-level variation among plants in structuring patterns of frugivore foraging and, thus, seed dispersal in a plant community. Here we use an animal perspective to examine how space and variation between individual plants affect movement and visitation by frugivores foraging on individual fruiting plants. To do this, we used a spatially explicit network approach informed by observations of the movement and foraging of a frugivorous lemur species (Eulemur rubriventer) amongst individual plants in a diverse plant community in Madagascar. The resulting hierarchical networks, in which a few individual plants received the bulk of the interactions, demonstrated how a generalist frugivore species could act as an individual-plant specialist within a plant community. The few individual plants that dominated interactions with the lemurs shaped the modular spatial structure of frugivory interactions in the community and facilitated visitation to near neighbors. This interaction structure was primarily driven by extrinsic factors, as lemur movements among plants were significantly influenced by the individual plant’s spatial position and the species richness of fruiting plants in its immediate neighborhood. Individual plants in central spatial locations, with a rich fruiting neighborhood and large fruit crops, received the most visits. The observed drastic inequality in the interactions of a generalist frugivore within a highly diverse plant community highlights the importance of considering individual-level variation for essential ecosystem processes, such as seed dispersal.