Effects of habitat complexity, prey type and abundance on intraguild predation between larval odonates

Intraguild predation has been shown to be important among terrestrial and aquatic arthropods and although this interaction has received considerable attention in terrestrial systems, much remains to be learned about factors affecting intraguild predation among aquatic insects. This manipulative study was designed to identify interactive effects among prey type, prey abundance and levels of habitat complexity on foraging success of predatory species and the strength of intraguild predation between larval Gomphaeschna furcillata (intraguild predator), and Enallagma civile (intraguild prey), two odonate species common in lentic water bodies of the southeastern U.S. Utilizing mesocosms, this study was developed as a 2 x 2 x 2 factorial design with two levels each of shared prey species (gammarid amphipods or Triops), shared prey abundance (low and high), and structural complexity of habitat (simple or complex). Survivorship and growth data for all odonates were recorded throughout the experiment. Those treatments containing a structurally complex habitat resulted in greater refuge space for shared prey organisms, increasing the frequency of intraguild predation. When shared prey consisted of Triops, a more active and visible invertebrate in the water column, shared prey consumption increased, lowering intraguild predation. Intraguild predation became more apparent in the mesocosms when shared prey abundances were low. Intraguild predation is likely to play a critical role in structurally complex aquatic habitats that support generalist predators, such as odonates, whose populations are size-structured in nature.