Predator phylogenetic diversity decreases predation rate via antagonistic interactions

12 Background: Predator assemblages can differ substantially in their topdown effects on 13 community composition and ecosystem function, but few studies have sought to explain 14 this variation in terms of the phylogenetic distance between predators. The effect of a local 15 predator assemblage will depend on three things – which predators tend to co-occur, how 16 similar their prey preferences are, and how they interact with each other and the whole 17 community. Phylogenetic distance between predators may correlate with each of these 18 processes, either because related predators are more likely to share the same traits, and 19 therefore have similar habitat and prey preferences, or because predators are more likely to 20 compete, and therefore diverge in habitat and prey preferences. Therefore, the phylogenetic 21 structure of predator assemblages could provide a unifying framework for predicting how 22 predators will impact their prey and therefore any ecosystem functions mediated by their 23 prey. 24 Methods: We examined the effects of predators on macroinvertebrate food webs found 25 in bromeliads, combining field observations, laboratory feeding trials and a manipulative 26 experiment. We determined whether the phylogenetic distance between predators could 27 explain: the co-observed occurrence of predator species among bromeliads, overlap in prey 28 preferences under no-choice conditions, and effects of predator composition on prey survival, 29 prey composition and ecosystem processes. 30 Results: We found that phylogenetic distance does not predict either the co-occurrence 31 of predator species nor the overlap in their prey preferences. However, our manipulative 32 experiment showed that prey mortality decreased as the phylogenetic distance between 33 2 . CC-BY 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/089144 doi: bioRxiv preprint first posted online Nov. 22, 2016;