Different adaptability of the brown planthopper, Nilaparvata lugens (Stål), to gradual and abrupt increases in atmospheric CO₂

Abstract

Increasing atmospheric CO₂ concentrations affect the performances of herbivores. Most previous studies have focused on the effects of abrupt increases in CO₂ concentration on herbivore performance, but knowledge about the response of herbivores to gradual increases in CO₂ is lacking. We tested the hypothesis that herbivores will show different responses to abrupt and gradual CO₂ increases. We measured the performance of the brown planthopper (BPH) (Nilaparvata lugens (Stål)) reared on rice for 15 successive generations under three CO₂ levels: ambient CO₂ (375 µl/L), a gradual increase in CO₂ (25 µl/L increase per generation, 390–750 µl/L), and an abrupt increase in CO₂ (750 µl/L). During the first generation, the female and male longevities were affected by both the gradual and abrupt increases in CO₂, and the fecundity and net reproductive rate (R₀) of the BPH in the abruptly increased CO₂ 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 CO₂ treatments. After 14 generations, female longevity was significantly prolonged in treatments with both gradual and abrupt CO₂ increases. The fecundity of the BPHs reared in the gradual CO₂ treatment was significantly higher than that in the other two CO₂ treatments. According to the population parameters (r, λ, and R₀) and population projection, under a gradual increase in CO₂, the BPH population size was higher than that under an abrupt CO₂ increase. We concluded that the BPH abundance will increase under a gradual CO₂ increase and consequently result in an increase in rice yield loss.