Journal
ENVIRONMENTAL ENTOMOLOGY
Volume 43, Issue 3, Pages 569-576Publisher
ENTOMOLOGICAL SOC AMER
DOI: 10.1603/EN13179
Keywords
sampling effect; diversity effect; biological control; Rhopalosiphum padi; Coleomegilla maculata
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Funding
- University of Missouri's Life Sciences Fellowship Program
- U.S. Department of Agriculture Agriculture and Food Research Initiative grant [2009-02083]
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Studies manipulating predator diversity and measuring the impact on herbivore abundance have found that enhancing predator species richness often increases the strength of prey suppression. This relationship may be due to mechanisms such as complementarity or facilitation, which are considered true benefits of diversity because greater prey suppression is an emergent property of the multispecies predator community. Or it may be due to an identity effect, an apparent benefit of diversity that results from the greater likelihood of including one particularly voracious predator species as the total number of predator species increases. In separate greenhouse and field experiments, we simultaneously manipulated the species richness and species composition of predators attacking bird cherry-oat aphids (Rhopalosiphum padi) (L.) on wheat (Triticum aestivum L.). We found that on average aphid suppression by species-rich predator assemblages was greater than suppression by single-species monocultures. However, the performance of individual predator species varied and the species-rich assemblages did not outperform all single-species compositions, suggesting an identity effect. In particular, single-species compositions of the lady beetle Coleomegilla maculata (DeGeer) exhibited high performance across experiments, and on average predator assemblages that contained a lady beetle predator had lower overall aphid abundance than compositions where lady beetles were absent. Taken together, these results provide evidence for the dominant role of lady beetles, especially C. maculata, in natural pest suppression and suggest that predator species composition and identity are important factors to consider in efforts to conserve this valuable ecosystem service.
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