1
non-additive effect of predators. (left) predator combinations may result in more (a) or less (b) prey mortality, with a corresponding change in decomposition. Prey behaviour (c) may be affected independently of density (left). (above) mean and 95% bootstrap confidence intervals for predator non-additive effects, calculated as mean(monoculture) - mean (polyculture) The effect of predator functional diversity on ecosystem function in a bromeliad food web A. Andrew M. MacDonald 1 , Diane S. Srivastava 1 and Gustavo Q. Romero 2 1. Department of Zoology, University of British Columbia, BC, Canada; 2. Main question: How does predator phylogenetic diversity (PD) alter the prey community, and in turn affect ecosystem function? Leptagrion Insecta Bilateria Diverse predator combinations result in less mortality but not less decompositon Methods and study system: Bromeliads (Quesnelia arvensis) contain a diverse community of invertebrates, forming a mostly detritus-based food web. Predators in this system range from damselflies (Odonata) in the genus Leptagrion, to fly larvae (Diptera:Tabanidae) and leeches. We stocked bromeliads with a standard prey community containing all major functional groups, forming a processing chain. Neither the presence nor the diversity of predators affects nitrogen cycling NMDS ordination of surviving prey communities. There is little evidence for a distinct diet difference between the predator compinations Predator treatments included single-species monocultures and two-species polycultures of increasing phylogenetic diversity Effects on nitrogen cycling: (above) Nitrogen cycling, measured as the amount of N 15 transferred into bromeliad leaf tissue from labelled leaves, differs little among treatments. (left) there is no evidence for nonadditive effects of predators. L. elongatum L. andromache Tabanid Leech Conclusions Polycultures of predators show a negative, non-additive effect on predation when PD his high. This is possibly due to an increase in interference or intraguild predation. There is little evidence for predator-mediated increase in Nitrogen cycling; however decomposition was also low in all treatments. Thank you! Aline Nishi, Robin LeCraw, Alathea Letaw Paula Omena and grad students of the Romero Lab a b c
