It is predicted that the current atmospheric CO2 concentration will be doubled and global mean temperature will increase by 1.5-6°C by the end of this century. Although a number of studies have addressed the separate effects of CO2 and temperature on plant-insect interactions, few have concerned with their combined impacts. In the current study, a factorial experiment was carried out to examine the effect of a doubling CO2 concentration and a 3°C temperature increase on a complete generation of the brown planthopper (Nilaparvata lugens) on rice (Oryza sativa). Both elevated CO2 and temperature increased rice stem height and biomass of stem parts. Leaf chlorophyll content increased under elevated CO2, but only in ambient temperature treatment. Water content of stem parts was reduced under elevated temperature, but only when coupled with elevated CO2. Elevated CO2 alone increased biomass of root and elevated temperature alone enhanced leaf area and reduced ratio of root to stem parts. Brown planthopper (BPH) nymphal development was accelerated, and weight of and honeydew excretion by the F1 adults was reduced under elevated temperature only. Longevity of brachypterous females was affected by a significant interaction between CO2 and temperature. At elevated temperature, CO2 had no effect on female longevity, but at ambient temperature, the females lived shorter under elevated CO2. Female fecundity was higher at elevated than at ambient temperature and higher at elevated CO2 than at ambient CO2. These results indicate that the combined effects of elevated temperature and CO2 may enhance the brown planthopper population size.

Genetic variation and patterns of genetic differentiation of the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), from the South China were analyzed using 6 microsatellite markers and two partial mtDNA (cox1 and cox2) regions. All of the 6 microsatellite loci were polymorphic in the studied seven populations. The allelic richness per population ranged between 5.67 and 14.00, and average HE and HO values were 0.6246-0.8329 and 0.2634-0.6061, respectively. As the mitochondrial genome is a single genetic locus, we only present results for the concatenated data set (cox1 plus cox2 gene sequences, 513 bp). The concatenated data showed high level of genetic diversity and there are 23 variable polymorphic sites among the 513 sites in concatenated data. Nearly all of (20 of 21) pairwise FST comparisons among populations showed genetic differentiation with moderate to high pairwise FST values based on microsatellite markers. However, for the mtDNA data, most of the seven populations did not show significant differentiation with other populations. The differences of population differentiation obtained with the two different genetic markers could be mainly attributed to the different mutation rates of microsatellite and mtDNA. There was not genetic structure existed in these studied populations based on microsatellite loci and mtDNA data. The analysis based on network, mismatch distribution, Tajima’s D and FS indicated that the studied populations were from the recent same ancestor or the same refuge and followed by a sudden demographic expansion condition.