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Atmospheric CO2 Enrichment Impacts Three Trophic Levels in a Study of Transgenic Cotton
Chen, F., Ge, F., and Parajulee, M.N.  2005.  Impact of elevated CO2 on tri-trophic interaction of Gossypium hirsutum, Aphis gossypii, and Leis axyridisEnvironmental Entomology 34: 37-46.

What was done
Transgenic Bacillus thuringiensis Berliner cotton (Gossypium hirsutum L. cv GK-12) plants were grown from seed for 30 days in well watered and fertilized sand/vermiculite mixtures in pots located in controlled-environment chambers maintained at atmospheric CO2 concentrations of 370, 700 and 1050 ppm.  Three generations of cotton aphids (Aphis gossypii Glober) were subsequently allowed to feed on some of the plants, while a subset of the aphid-infected plants was additionally supplied with predatory ladybugs (Leis axyridis Pallas).  Throughout this complex set of operations, several types of measurements were made on both the aphids and the ladybugs.

What was learned
The authors found that (1) "plant height, biomass, leaf area, and carbon:nitrogen ratios were significantly higher in plants exposed to elevated CO2 levels," (2) "more dry matter and fat content and less soluble protein were found in A. gossypii in elevated CO2," (3) "cotton aphid fecundity significantly increased ... through successive generations reared on plants grown under elevated CO2," (4) "significantly higher mean relative growth rates were observed in lady beetle larvae under elevated CO2," and (5) "the larval and pupal durations of the lady beetle were significantly shorter and [their] consumption rates increased when fed A. gossypii from elevated CO2 treatments."

What it means
Chen et al. say their study "provides the first empirical evidence that changes in prey quality mediated by elevated CO2 can alter the prey preference of their natural enemies," and in this particular case, they found that this phenomenon could "enhance the biological control of aphids by lady beetle."

Reviewed 18 May 2005