Artificial Diversity of Plant – Insect Communities and Modern Crop Stoichiometry in Small Closed Patches in Greenhouse

Abstract

Little is known about the effect of artificial diversity of plant – insect communities on the carbon and nitrogen stoichiometry, weight, and water content of the modern crops. Using a microcosm experiment with two closely related crop species ( Brassica napus and B. juncea ), the sap feeder turnip aphid ( Lipaphis erysimi ), the folivore diamondba ck moth ( Plutella xylostella ) and its larval - pupal parasitoid wasp, Diadegma semiclausum , the Shannon biodiversity index was evaluated and regressed to the experimental data of carbon and nitrogen stoichiometry, water content and weight of the crops. Carbo n: Nitrogen (C:N) ratio of the modern cultivar under single planting had a logarithmic relationship with the artificial biodiversity index, while this relationship under plant interference was linear and positive. Water content of both experimental crops c hanged with the artificial biodiversity index conversely under single planting setup. When insects (either the folivore or the phloem feeder) damaged the host plants, the weight and water content of both crop species were 1.8 – 4.1 times higher than the co ntrol treatment. Apart from being a recurrent demonstration of the plant tolerance against insect feeding activity, current results can take a step forward for developing a theory on functional artificial biodiversity after herbivore insect – crop interactio ns. Keywords: C:N balance, Diamondback moth, Species richness, Shannon index, Stoichiometric analysis