|Gable, Jacob -|
|Crowder, David -|
|Northfield, Tobin -|
|Snyder, William -|
Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 7, 2012
Publication Date: September 1, 2012
Citation: Gable, J., Crowder, D., Northfield, T., Steffan, S.A., Snyder, W. 2012. Niche engineering reveals complementary resource use. Ecology. 93(9):1994-2000. Interpretive Summary: Altogether, our results provide evidence that arthropod herbivory can mediate predator diversity effects. In our greenhouse study, predator diversity effects were strong when caterpillars were absent, and appeared to be driven largely by complementarity. When caterpillars were present, however, predator diversity effects disappeared, and single, highly-effective predator species had the greatest impact on aphids. Paired with the observed effects of caterpillar feeding damage on predator foraging behavior, this strongly suggests that spatial-niche differences among predator species determine whether emergent diversity effects will occur. Our open-field observations suggested that this flexibility in whether predators complement one another or not, might lead to a mosaic of emergent diversity effects arising and disappearing across landscapes. This supports the growing realization that consumers may complement one another in one particular ecological situation, but not in another. Impact Statement: From the farm to the unmanaged system, we often struggle to predict and/or react to changes in biodiversity. Basic information about how species interact within an ecosystem improves our management and enjoyment of the goods and services provided by that system. Our study advances the understanding of how ecosystem engineering by herbivorous arthropods can shape the functioning of a system.
Technical Abstract: Greater resource use by diverse communities might result from species occupying different, complementary niches. Niche partitioning is difficult to directly demonstrate, however, because differences among species in the resources they use are often difficult to separate from other species-specific traits (e.g., size, feeding rate, phylogeny). Here, we overcame this difficulty by exploiting plastic foraging behavior in a community of predatory insects. These predators complemented one another by partitioning foraging space on leaves, with some species foraging primarily along leaf edges and others at leaf centers. On intact leaves, edge- and center-foraging predators combined to kill more prey than any single predator species could on its own. These emergent diversity effects, however, disappeared on plants damaged by the caterpillar Plutella xylostella. Caterpillar chew-holes brought edge micro-habitats to the center of leaves, such that all predator species could attack aphids anywhere on the plant. With niche differences diminished, there were no benefits of predator diversity, as the most voracious single predator species killed the most aphids. Thus, caterpillar herbivory determined whether the combined impacts of multiple predator species reflected complementarity or species’ individual effects. Our study provides direct evidence for a causative relationship between niche differences and increased resource consumption by diverse communities. Ecological engineers revealed this relationship by homogenizing the foraging environment and lessening niche separation among consumers.