Trophic energy flows increase in more diverse communities of coastal food webs: Testing the vertical diversity hypothesis

Biomass is a common, universal indicator of ecosystem productivity for exploring biodiversity–ecosystem functioning (BEF) relationships in all types of ecosystems. However, positive BEF is often missing in aquatic consumer communities with multitrophic interactions. Here, we apply a new indicator, integrated trophic position (iTP), which is defined as the summed TPs of all consumers weighed by the relative biomass of each taxon, for multitrophic systems to test the vertical diversity hypothesis (VDH) that functional diversity can enhance trophic energy flows within a food web. Using a meta-community of coastal benthic macroinvertebrates, we demonstrate that iTP increases in more diverse communities, supporting the VDH. Comparing our results with previous findings that stream benthic macroinvertebrates exhibit a negative BEF in contrast to the VDH, we discuss a possible mechanism to explain this contrasting pattern. Finally, we use a size-based food web approach to deepen our mechanistic understanding of the observed BEF.