COS 126-5 - Distinct functional responses of consumers and their producers to climate drive ecological network specialization

Abstract: Ecosystem function is supported by the complexity of species traits and species interactions in multitrophic assemblages. In multitrophic assemblages of producers and consumers, the trait composition of species at one trophic level can influence the trait composition of species at the other trophic level, e.g., via trait matching in species interactions. However, abiotic variation along large-scale environmental gradients can show different constraints on species traits and functional composition of species assemblages at different trophic levels, setting asymmetric limits to trait matching and the availability of interaction-relevant traits. Here, we test whether large-scale climatic gradients influence network specialization via changes in interaction-relevant traits at different trophic levels. We integrated data on species distributions, traits and species interactions of consumers (mammalian frugivores) and their producers (palms) to quantify functional trophic asymmetry, i.e. the relative divergences between consumer and resource assemblages in their functional trait richness and evenness. We then relate functional trophic asymmetry to geographic variation in climate and test whether it influences network specialization and how this varies among biogeographic regions. We found high levels of functional trophic asymmetry in regions of high annual precipitation. Furthermore, variations in functional trophic asymmetry cascade influence network specialization, making plant-frugivore networks less specialized in regions where functional trophic asymmetry is high. Our work expands community-scale analysis of trait-environment relationships to cover multitrophic levels and identifies novel mechanisms of how functional diversity between trophic levels influences network structure. Thus, providing a way to test the links between the multitrophic effects of climate change in functional diversity and changes in the function of ecosystems.