The effects of plant community diversity on insect dynamics and ecosystem stability

The biodiversity-ecosystem functioning hypothesis states that a reduction in biodiversity will cause a reduction in ecosystem level processes. In a caged greenhouse experiment, this study examined the relationship between the temporal variability of individual species abundances as a measure of ecosystem stability at different levels of plant diversity. Plant communities were assembled from a pool of 4 plant species tomato Lycopersicon esculentum Mill. (Solanaceae), pepper Capsicum annuum L. (Solanaceae), eggplant Solanum melongena L. (Solanaceae), and mullein Verbascum thapsus L. (Scrophulariaceae) according to two treatments: monocultures (low diversity) and polycultures (high diversity). Low and high diversity treatments received the same number of insects in the same combination: two herbivores greenhouse whitefly Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) and western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), a parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) and a predatory mite Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) and a generalist predator Dicyphus hesperus Knight (Heteroptera: Miridae). Temporal stability was calculated for individual species and the entire community and plant diversity effects on insect density were assessed using repeated measures analyses of variance.