Meeting Abstract
75.1 Friday, Jan. 7 Sequential predator effects across life stages: Predicting phenotypic and density effects of egg predators on larval survival and growth VONESH, J.R.*; MCCOY, M.W.; HUGHEY, M.C.; WARKENTIN, K.M.; Virginia Commonwealth Univ.; Virginia Commonwealth Univ.; Boston Univ.; Boston Univ. jrvonesh@vcu.edu
Most species have complex life cycles during which they are vulnerable to different suites of predators as they shift habitats through ontogeny. While these predators do not interact directly because they are separated in time and space, they may still interact indirectly via their effects on the density and traits of their shared prey. Here we examine sequential predator effects on the leaf-breeding treefrog, Agalychnis callidryas. Arboreal egg predators reduce initial tadpole density and also induce embryos to hatch earlier at smaller sizes. We explore how these egg predator effects play out through the larval stage. First, we predicted the effects of sequential predators on larval mortality and growth to 30 days using simulations. These simulations were parameterized from short term experiments that allowed us to quantify tadpole size- and density-specific growth and mortality in the presence or absence of a common aquatic tadpole predator, a giant water bug. We then compared these predicted results with those observed in a mesocosm experiment where we manipulated hatchling size and density, and aquatic predator presence. As predicted by simulations, water bugs consumed 40-60% of tadpoles by day 30. Egg predator induced early hatching had no long term effect on survival, while reduced initial tadpole densities reflecting egg predation increased larval stage survival. Models tended to underestimate larval growth, but accurately captured treatment patterns. Hatching early and at initial lower densities both tended to increase final size, as predicted. Our results highlight that by developing a functional understanding of the relationships between prey size and density and their effects on mortality and growth we can develop a predictive framework for understanding sequential predator effects.
