Multiple Factors Influence the Strength of Intraguild Interactions
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Date
2011
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Authors
Davenport, Jon M.
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East Carolina University
Abstract
Species engaged in intraguild predation (IGP) not only compete for the same food resources but can also eat each other. In some cases, a predator species in a higher trophic position (i.e., a top predator) can eat a predator species with an intermediate trophic position (i.e., an intermediate predator) but the intermediate predator cannot consume the top predator. An important question in ecology is how can intermediate predators persist with top predators that both eat and compete with them? I examined how environmental complexity (food web complexity, variability in the kinds of environmental cues that elicit behavioral/morphological responses of predators, and habitat complexity) affects the strength of IGP within temporary ponds. To do this, I conducted experiments in artificial ponds and focused on interactions between larval dragonflies (Anax spp., a top predator) and larval salamanders (Ambystoma opacum, an intermediate predator). Salamander survival was consistently reduced by dragonflies but the effect of dragonflies on salamander survival was enhanced in structurally complex environments that facilitated the ambush hunting style of dragonflies. The provision of either more prey individuals or alternative prey species did not diminish the effect of dragonflies on salamander survival. Salamanders did alter their behavior and morphology in response to dragonflies in ways that reduced their mortality risk to dragonflies. A high abundance of conspecifics, however, reduced the extent to which salamanders alter their morphology. Larval salamander growth, a trait that affects fitness of adults, was also affected by environmental complexity. Although the abundance and kinds of prey available had no effect on salamander survival, they enhanced the positive effect dragonflies had on salamander growth by ensuring survivors had more high quality food to eat. Morphological responses of salamanders to dragonflies did not cause a reduction in the foraging ability of salamanders. These results support the hypothesis that environmental complexity can alter the strength of IGP interactions. Although I have not found support for theory which attempts to explain how intermediate predators can persist in food webs with top predators, the results from my dissertation highlight the environmental conditions that promote the likelihood of coexistence between predators involved in IGP.
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Biology, Ecology, Zoology, Biology, Zoology, Biology, Ecology