Abstract
It is predicted that the current atmospheric CO2 level will be doubled by the end of this century. Here, we investigate the impacts of elevated CO2 (550 and 750 μL/L) on the development and nutrition status of the green pea aphid for six generations, which is longer than previous studies. All seven examined physiological parameters were not affected over six generations under the ambient CO2 level (380 μL/L). However, the elevated CO2 levels (550 and 750 μL/L) prolonged nymph duration, decreased adult longevity, female fecundity and protein content, and increased the contents of total lipid, soluble sugar and glycogen. There was a significant interaction between the effect of CO2 levels and the effect of generations on nymph duration, female fecundity and adult longevity. The elevated CO2 had immediate effects on the female fecundity and the contents of total protein, total lipid and soluble sugar, starting within F0 generation. The adult longevity decreased, and the glycogen content increased from the F1 generation. However, the significant effect on the nymph development was only observed after three generations. Our study indicates that the elevated CO2 levels first influence the reproduction, the nutrition and the energy supply, then initiate aphid emergency responses by shortening lifespan and increasing glucose metabolism, and finally result in the slow development under further persistent elevated CO2 conditions after three generations, possibly leading to population decline under elevated CO2 conditions. Our results will guide further field experiments under climate change conditions to evaluate the effects of elevated CO2 on the development of the pea aphids and other insects, and to predict the population dynamics of the green pea aphid.
Highlights
A rise in atmospheric carbon dioxide (CO2) concentration is the most conspicuous characteristics of global climate change in this century (Michael, 2019)
There was a statistically significant interaction between the effects of CO2 level and generation on the nymph duration (F = 36.3; df = 10; p < 0.001; Table 1). This indicates that the effect CO2 levels on nymph duration is dependent on the generation, and the nymph duration at each generation is dependent on the CO2 levels
Significant interactions were found for the measurements of adult longevity (F = 13.1; df = 10; p < 0.001), female fecundity (F = 17.3; df = 10; p < 0.001), protein content (F = 20.3; df = 10; p < 0.001) and sugar content (F = 9.5; df = 10; p < 0.001; Table 1)
Summary
A rise in atmospheric carbon dioxide (CO2) concentration is the most conspicuous characteristics of global climate change in this century (Michael, 2019). The effects of elevated atmospheric CO2 concentration on plant nutritional and defensive chemistry, and their consequent effects on insect have received extensive attention (DeLucia et al, 2012; Facey et al, 2014). The concentrations of phenolics, terpenoids, condense tannins, and gossypol were increased in Gossypium hirsutum by elevated CO2 (Coviella et al, 2002). The elevated CO2 mediated the decrease of plant N content resulting in a nutritional deficiency for protein-limited insect pests (Mattson, 1980; Coviella and Trumble, 1999) and reduced fecundity and fitness of most leafchewing insects (Coll and Hughes, 2008). Insect responses to rising CO2 are not uniform. Robinson et al (2012) found that while Lepidoptera populations decreased with elevated CO2, the populations of other groups such as Homoptera and Acari increased
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