Meeting Abstract

55.7  Tuesday, Jan. 6  Morphological Responses to Abiotic and Biotic Factors: Temperature Effects on Predator-Induced Phenotypes in a Neotropical Treefrog Tadpole TOUCHON, Justin C.*; WARKENTIN, Karen M.; Boston University, Dept. of Biology; Boston University, Dept. of Biology jtouchon@bu.edu

Predator-induced phenotypic plasticity is well-known. However, the adaptive value of induced defensive phenotypes can vary. Abiotic factors affect larval growth rate, changing how long prey are vulnerable to predators and the relative value of investment in growth or defense. Thus, larval investment in predator-specific defensive phenotypes may be affected by abiotic conditions. Tadpoles of the Neotropical treefrog Dendropsophus ebraccatus change tail shape and coloration in response to predators. We studied the influence of growth rate, affected by pond temperature, on the development of predator-induced defensive phenotypes of D. ebraccatus tadpoles. First, we obtained realistic estimates of variation in growth rate by raising tadpoles in cages in sunny and shaded areas of four ponds, spanning a range of water temperatures. We monitored tadpole growth every week until metamorphosis and correlated growth rates with pond temperature. Tadpole growth rates varied both between sunny and shaded sites within ponds and between ponds. Using temperatures from our field study, we conducted a 2 X 2 factorial experiment in the lab, crossing slow and fast growth rates with the presence or absence of a caged larval predator. We conducted the experiment twice, using early and late larval-stage predators (Libellulid and Belostomatid, respectively). We measured the onset and outcome of phenotype induction by digitally photographing tadpoles at three intervals during each experiment. Tadpole morphology varied with both predator exposure and temperature, and predator effects differed with temperature. Natural variation in both abiotic and biotic factors thus generates a diversity of functionally different tadpole morphologies.