PARENT SESSION
Oral Session #18: Predator-Prey Interactions: Plants and animals. Presiding: B. Goodwin.
Monday, August 6, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.
Complex habitats moderate predator-predator interactions and dampen trophic cascades.
Langellotto, Gail1, Denno, Robert1, 1
ABSTRACT- That habitat structure is of primary importance in determining spider community structure and spider abundance has repeatedly been demonstrated by both correlative and experimental studies. Because spiders are generalist predators that often prey upon one another (intraguild predation), the extent to which these predators can coexist may strongly depend on their ability to move and hide within their environment. Complex habitats have the potential to provide refuge from predation, and thus may explain the positive association of spiders with structurally complex versus simple habitats. The potential of complex habitats to reduce intraguild predation was addressed in a pair of field experiments that used a guild of wolf spiders (Pardosa littoralis and Hogna modesta) that inhabit an intertidal marsh. The habitat component which we manipulated to create simple and complex habitats was leaf litter thatch. The first experiment assessed how thatch mediates cannibalism when low and high densities of Pardosa are offered alternative prey. The second experiment was a field assessment of how thatch mediates intraguild predation of Pardosa by Hogna. The results of the first experiment suggest that cannibalism is not a significant mortality factor in Pardosawolf spiders. However, the results of the second experiment show that intraguild predation has the potential to significantly reduce Pardosa population size and that access to a complex, thatch-containing habitat significantly moderates agonistic predator-predator interactions. These results suggest that structurally complex habitats diminish the potential for trophic cascades by reducing the potential effect of higher order predators on lower trophic levels.
KEY WORDS: intraguild predation, habitat complexity, trophic cascade