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Virginia Commonwealth University VCU Scholars Compass Biology Presentations Dept. of Biology 2010 Interactions between competition and predation shape early growth and survival of two Neotropical hylid tadpoles [poster] Sergio C. Gonzalez University of Florida Justin C. Touchon Boston University James R. Vonesh Virginia Commonwealth University, [email protected] Follow this and additional works at: http://scholarscompass.vcu.edu/biol_present Part of the Ecology and Evolutionary Biology Commons Downloaded from http://scholarscompass.vcu.edu/biol_present/4 This Presentation is brought to you for free and open access by the Dept. of Biology at VCU Scholars Compass. It has been accepted for inclusion in Biology Presentations by an authorized administrator of VCU Scholars Compass. For more information, please contact [email protected]. Interactions between competition and predation shape early growth and survival of two N eotropical hylid tadpoles Sergio C. Gonzalez 1 ([email protected]), Justin C. Touchon2 ([email protected]), and James R. Vonesh3 ([email protected]) lUniversity of Florida, 2Boston University & STRI, 3Virginia Commonwealth University Introduction No predator The relative importance of competition and predation in shaping communities is a long standing question in ecology. Past studies show that competition typically has stronger effects on growth, whereas predator presence has stronger effects on survival. Further, predators often modify the effects of competitors. The interaction of these factors is particularly important for anuran larvae; predators typically reduce the effect of competition on growth and the presence of alternative prey may also alter predation on focal taxa. 1.0 C S - .0 0.8 • A. cal/idryas grew faster and o. ebraccatus slower when they co-occurred in the absence of predators. Aga/ychnis cal/idryas c::::::::J Oendropsophus ebraccatus 0.8 0.6 0.6 ~ 0.4 0.4 • Predators substantially reduced tadpole growth, despite more than doubling per capita food avail ability by consuming >60% of tadpoles 0.2 • Predation erased competitive asymmetry 0.0 • Mortality of both species with the predator was reduced by the presence of the other species -0.. ro t o 0.2 ~ Question: What are the independent and combined effects of competition and predation on the survival and growth of tadpoles of two co-occurring hylid frogs? 0.40 0.40 (])? +-' -t-' roO> s..... C - Agalychnis cal/idryas: large mid-water filter feeder - Oendropsophus ebraccatus: smaller algal grazer • Q) ~ .~ 0.30 0.30 coc O~ s.......c Methods u:::: a 0)0, (]) c No Predator Predator Q) >- .cu 0.20 -t-' ._ • 2 x 3 randomized factorial design • predator presence or absence • 1 Anax amazili dragonfly larva • tadpole species composition • 50 A. cal/idryas } All same • 50 O. ebraccatus oviposition • 25 of each species cohort • 1: 1 mixture of suspended and benthic food . 6 replicates in 400 L mesocosms over 8 days • Main and interactive effects of species identity, species composition, and predator presence examined using GLM (mortality) and LM (growth) Results • Both species had similar growth when alone 1.0 . pecles t o o0.. s..... Predator • We show that predator effects can dominate both survival and growth • These results highlight the potential importance of predators in shaping prey populations and aquatic food web interactions in the tropics via both direct (]):::.- 0:::8' 0.10 0.10 Single A-. callidryas 0 and B. ebraccatus tadpoles at start of experiment. ' _ Conclusions & Significance 0.20 ro:!: - c , • No evidence of predator preference for prey type Mixed Single Mixed Figure 1. Mortality and growth rates of Agalychnis cal/idryas and Oendropsophus ebraccatus tadpoles in single and mixed species treatments in the presence and absence of predaceous Anax amazili nymphs. Inset: Final size distribution of tadpoles in predator and no predator treatments. Mortality - Pred: P < 0.001, Composition: P < 0.001, Spp*Pred: P < 0.001 Growth - Pred: P < 0.001, Spp*Composition: P < 0.001, Spp*Pred: P < 0.001 Acknowledgments We thank Karen M. Warkentin, Venetia S. Briggs, Max A. Nickerson, Christopher M. Asquith and the 2009 Vonesh-Warkentin Gamboa, Panama research group. The Autoridad Nacional del Ambiente de Panama gave permission to conduct this research (Permiso SE/A-41-08). This work was funded by a National Science Foundation (USA) Research Experience for Undergraduates (REU) supplement to DEB-0717220 (JRV), NSF DEB-0716923 (KMW) , the Smithsonian Tropical Research Institute, Virginia Commonwealth University, Boston University, and the University of Florida's University Scholars Program. Smithsonian Tropical Research Institute