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Responses of multiple generations of Gastrophysa viridula, feeding on Rumex obtusifolius, to elevated CO 2
Author(s) -
Brooks G. L.,
Whittaker J. B.
Publication year - 1998
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.1998.00111.x
Subject(s) - fecundity , zoology , relative growth rate , biology , larva , hatching , instar , horticulture , toxicology , botany , growth rate , population , medicine , geometry , mathematics , environmental health
Rumex obtusifolius plants and three generations of the tri‐voltine leaf beetle Gastrophysa viridula were simultaneously exposed to elevated CO 2 (600 ppm) to determine its effect on plant quality and insect performance. This exposure resulted in a reduction in leaf nitrogen, an increase in the C/N ratio and lower concentrations of oxalate in the leaves than in ambient air (350 ppm). Despite these changes in food quality, the effect of elevated CO 2 on larvae of Gastrophysa viridula over three generations was minimal. However, the effect of CO 2 did differ slightly between the generations of the insect. For the first generation, the results obtained were different from many of the published results in that elevated CO 2 had no measurable effects on performance, except that third instar larvae showed compensatory feeding. Food quality, including leaf nitrogen content, declined over time in material grown in both ambient and elevated CO 2 . The results obtained for the second generation were similar to the first except that first instar larvae showed reduced relative growth rate in elevated CO 2 . Development time from hatching to pupation decreased over each generation, probably as a result of increasing temperatures. Measurements of adult performance showed that fecundity at the end of the second generation was reduced relative to the first, in line with the reduction in food quality. In addition at the end of the second generation, but not at the end of the first generation, adult females in elevated CO 2 laid 30% fewer eggs per day and the eggs laid were 15% lighter than those in ambient conditions. These lighter eggs, coupled with no effect of elevated CO 2 on growth during the third generation, meant that the larvae were consistently smaller in elevated CO 2 during this generation. These results offer further insights into the effect that elevated CO 2 will have on insect herbivores and provide a more detailed basis for population predictions.