PARENT SESSION
Poster Session #55: Plant-Animal Interactions II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Meta-analytical synthesis of the response of invertebrate natural enemies to complex-structured habitats .

Langellotto, Gail^*,1,2, Denno, Robert¹, ¹ University of Maryland, College Park, MD² University of California-Davis, Davis, CA

ABSTRACT- Here, we conduct a meta-analytical synthesis of the response of natural enemies invertebrate predators and parasitoids) to habitat complexity (number different structural elements / unit habitat volume) in terrestrial systems using data from 34 studies, reporting 47 independent tests. The standardized mean difference (Hedge's d) in the densities of natural enemies in simple- compared to complex-structured habitats was quantified for each individual study before the cumulative meta-analysis was conducted. Studies used in the meta-analysis varied at two spatial scales (habitat and within-plant) and comprised a diverse array of natural-enemy taxa (the natural-enemy assemblage at large, the entire spider assemblage, web-building spiders, hunting spiders, mites, hemipterans, predaceous beetles, ants, and parasitoids). The effects of both increases and decreases in habitat structural complexity (vegetation, detritus, and plant architecture) on natural enemy abundance were analyzed. For all taxa combined, increasing habitat structure resulted in a large and significant increase in natural enemy abundance. Similarly, experimentally decreasing habitat structure significantly diminished natural enemy abundance across all studies. Also, separate meta-analyses at both spatial scales (habitat and within-plant) found that increasing habitat complexity resulted in significant increases in natural-enemy abundance. In particular, manipulating levels of detritus at the habitat spatial scale had the strongest effect on natural enemy abundance. When data were analyzed according to natural enemy guild, hunting spiders were found to have the strongest positive response to increases in habitat complexity. Web-building spiders showed the strongest negative response to decreases in habitat complexity. Mechanisms underlying the accumulation of natural enemies in complex-structured habitats (e.g. diminished cannibalism and intraguild predation) are discussed, as are its consequences for ecological theory and the management of agricultural pests.

KEY WORDS: meta-analysis, habitat complexity