Different adaptability of the brown planthopper, Nilaparvata lugens (Stål), to gradual and abrupt increases in atmospheric CO 2

Increasing atmospheric CO 2 concentrations affect the performances of herbivores. Most previous studies have focused on the effects of abrupt increases in CO 2 concentration on herbivore performance, but knowledge about the response of herbivores to gradual increases in CO 2 is lacking. We tested the hypothesis that herbivores will show different responses to abrupt and gradual CO 2 increases. We measured the performance of the brown planthopper (BPH) ( Nilaparvata lugens (Stål)) reared on rice for 15 successive generations under three CO 2 levels: ambient CO 2 (375 µl/L), a gradual increase in CO 2 (25 µl/L increase per generation, 390–750 µl/L), and an abrupt increase in CO 2 (750 µl/L). During the first generation, the female and male longevities were affected by both the gradual and abrupt increases in CO 2 , and the fecundity and net reproductive rate ( R 0 ) of the BPH in the abruptly increased CO 2 treatment were significantly lower than those in the other two treatments; there were no significant differences in the intrinsic rate of increase ( r ) and the finite rate of increase ( λ ) among the three CO 2 treatments. After 14 generations, female longevity was significantly prolonged in treatments with both gradual and abrupt CO 2 increases. The fecundity of the BPHs reared in the gradual CO 2 treatment was significantly higher than that in the other two CO 2 treatments. According to the population parameters ( r , λ , and R 0 ) and population projection, under a gradual increase in CO 2 , the BPH population size was higher than that under an abrupt CO 2 increase. We concluded that the BPH abundance will increase under a gradual CO 2 increase and consequently result in an increase in rice yield loss.