Effects of Alternanthera philoxeroides Grown in Different CO₂ Environment on the Reproductive Ability of Agasicles hygyophila

To understand the indirect effects of elevated CO₂ concentrations on the growth, development and population reproduction of A. hygrophila, Age-stage two-sex life table of A. hygrophila feeding on A. philoxeroides grown in different CO₂ concentrations were constructed. The results showed that, as the CO₂ concentration increasing, the development duration was shortened, the oviposition period was lengthened, and the fecundity increased of A. hygrophila feeding on A. philoxeroides grown in correspond CO₂ environment. So it's indirectly beneficial for the fecundity of A. hygrophila. In the same CO₂ concentration (420 μL·L^-1) condition, the oviposition period and the fecundity of F5 were less than those of F1, but the development duration was lengthened. This indicated that the fecundity of A. hygrophila was declined with generation development under laboratory conditions. In the 420 μL·L^-1 CO₂ concentration condition, the net reproductive rate (R₀), intrinsic rate of increase (r) of F5 were less than F1, and the R₀ and r of F5 in 750 μL·L^-1 CO₂ concentration condition were also less than F1, but higher than that of F5 in 420 μL·L^-1 CO₂ concentration. The finite rate of increase (λ) and mean generation time (T) had no significant differences. The fertile female ratio at higher concentration was significantly higher than those at lower concentration. These results indicated that the reproductive of A. hygrophila feeding on A. philoxeroides grown in elevated CO₂ concentrations may be enhanced and the elevated CO₂ concentrations plays a positive effect on the growth and the development of A. hygrophila population.