Abstract
We evaluated the direct effects of three different atmospheric CO2 concentrations (380 ppm, 550 ppm and 750 ppm) on the population parameters of the cotton bollworm, Helicoverpa armigera fed an artificial diet. The life history and fitness of H. armigera were analyzed using an age-stage, two-sex life table. Our results showed significantly longer larval durations and lower female pupal weight under elevated CO2 than under ambient CO2. Additionally, the fecundity of H. armigera was lower under elevated CO2 than under ambient CO2. H. armigera reared under elevated CO2 conditions showed lower intrinsic and finite rates of increase but higher net consumption and finite consumption rates than H. armigera reared under ambient CO2 conditions. According to population projections, a much smaller total population size and reduced consumption capacities would be expected in an elevated CO2 atmosphere due to higher mortality and lower growth rate compared with ambient CO2 levels. These results indicate that the fitness of and potential damage caused by H. armigera would be affected by increased CO2 relative to ambient CO2 concentrations. Additional studies on the long-term direct and indirect effects of elevated CO2 levels on H. armigera are still needed.
Highlights
No significant differences were observed in the pre-oviposition periods (APOP) of female adults reared under the three CO2 concentrations, the longest total pre-oviposition period (TPOP, which includes the pre-adult period) of H. armigera was observed in the 750 ppm treatment group (27 d)
Most previously published studies focusing on the indirect effects of elevated CO2 on the life tables, consumption rates and population dynamics of herbivorous insects have been based on the traditional female-based, age-specific life table[17,18,19]
The present study measured the direct effect of elevated CO2 on the fitness and consumption rate of H. armigera using an age-stage, two-sex life table instead of the traditional female age-specific life table
Summary
A much smaller total population size and reduced consumption capacities would be expected in an elevated CO2 atmosphere due to higher mortality and lower growth rate compared with ambient CO2 levels These results indicate that the fitness of and potential damage caused by H. armigera would be affected by increased CO2 relative to ambient CO2 concentrations. Ambient carbon dioxide concentrations had increased to as high as 380 ppm by 2005 and have been predicted to reach at least 550 ppm by the year 2050 and to double by the end of the 21st century due to continuing high levels of fossil fuel consumption and various agricultural practices[4] This increase may directly affect plants by altering the chemical composition of the air, resulting in modifications to plant secondary metabolism[5]. Because development rates vary widely in a population, stage differentiation is critical to understanding the population ecology of insect herbivores[13]
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