The Effects Of Different CO₂ Concentrations On Age-stage, Two-sex Life Table And Symbiotic Bacteria Diversity Of Nilaparvata Lugens

With the elevation of atmospheric CO₂ concentration,the agricultural ecosystem had to some extent been affected,not only the growth and nutritional structure of crops had been directly changed,but also the agricultural pests had been indirectly affected.In the present study,we used two-sex life table method to analyze the differences in growth,reproduction,survival rate and population dynamics of continuous feeding brown planthopper?Nilaparvata lugens St?l?under ambient CO₂concentration?380?L/L?,intermediate concentration?550?L/L?,and double ambient CO₂ concentration?750?L/L?.Combined with 16S rDNA sequencing,we then compared the diversity and richness of the brown planthopper symbiotic bacteria under three different CO₂ concentrations.Based on COG function prediction and KEGG metabolic pathway analysis,we aimed to reveal the adaptation mechanism of brown planthopper under different CO₂ concentrations.The results are as follows:1.Life history and population dynamics of N.lugens reared under elevated CO₂After the N.lugens was continuously fed on rice under 3 different CO₂concentrations,ambient CO₂ concentration?380?L/L?,intermediate concentration?550?L/L?,double ambient CO₂ concentration?750?L/L?,we employed the 32nd generation N.lugens to determine their differnces in developmental time,reproduction,population dynamics.Our results revealed that the developmental time of nymphs and total pre-ovipositional period were significantly shortened under 550?L/L than those in double ambient CO₂ concentration and ambient CO₂concentration?P<0.05?,but there was no significant difference between the latter two concentration?P>0.05?,except 5th nymph developmental time was significantly shortened?P<0.05?.The elevated CO₂ concentration increased the survival rate of nymphs,and adult longevity was significantly increased under intermediate CO₂concentration?P<0.05?.The fecundity of N.lugens under intermediate CO₂concentration 550?L/L was significantly higher than those under the other two treatments?P<0.05?,but there was no difference between ambient and double ambient CO₂ concentration.We made a simulation of population dynamics for N.lugens under each CO₂ concentration.We found that the intrinsic rate of increase,finite rate of increase and net reproduction rate under 550?L/L were significantly higher than the other two treatments?P<0.05?,but there were no significant difference between ambient and double ambient CO₂ concentration?P>0.05?.Finally,there were no significant difference in the mean generation time among the three treatments?P>0.05?.2.The effect of long-term double ambient CO₂ concentration on the evolution of N.lugensAfter the N.lugens was continuously fed on rice 49 generations under the double ambient CO₂ concentration?750?L/L?,we used the two-sex life table theoretical analysis to compare the differences in developmental time,reproduction,population dynamics between the double ambient CO₂ concentration and blank control.We found that the 5th nymph development time was significantly shortened under double ambient CO₂ concentration?P<0.05?,but there were no significant differences in adult pre-oviposition period,total pre-oviposition period and other nymph development time?P>0.05?.The adult longevity was significantly shortened under double ambient CO₂ concentration?P<0.05?.There was no significant difference in survival rate of the nymphs at different stage between the two treatments?P>0.05?,but the survival rate of female was higher than male under double ambient CO₂concentration and opposite in the blank control.There were no significant differences in the intrinsic rate of increase,finite rate of increase and net reproduction rate between the two treatments?P>0.05?,but the mean generation time under double ambient CO₂ concentration was significantly shortened than blank control?P<0.05?.3.Effect of elevated CO₂ concentration on the symbiotic bacteria diversity of N.lugensBased on 16S rDNA sequencing,we analyzed the symbiotic bacteria diversity of N.lugens under three CO₂ concentrations,and found that the OTU value of the symbiotic bacteria slightly higher in the intermediate CO₂ concentration,indicating that the symbiotic bacteria richness was higher than other CO₂ concentration.The dominant bacteria under the three CO₂ concentration treatments belong to the same phylums like Proteobacteria,Actinobacteria and Firmicutes.Similarly,they were from the same genus like Acinetobacter,Staphylococcus,Aeromonas,Arthrobacter,Microbacterium.Although there were some differences in the richness of different taxons,but the diversity of the bacteria were the same.We also found the symbiotic bacteria of N.lugens involve in most of its physiological metabolism through COG function prediction and KEGG metabolic pathway analysis.The results showed that the abundance value of most metabolic pathway was the highest under intermediate CO₂ concentration.It indicated that the intermediate CO₂ concentration had a certain promoting effect on the physiological metabolism of N.lugens.4.The qRT-PCR of the dominant bacteria under elevated CO₂ concentration and the function exploration of AcinetobacterWe selected four dominant bacteria Acinetobacter,Aresenophonus,Arthrobacter,Chryseobacterium to take qRT-PCR.The results suggested that the relative density of Acinetobacter was the lowest under the ambient CO₂ concentration,but there was no difference in Arsenophonus among three CO₂ concentration treatments.The Arthrobacter of intermediate CO₂ concentration was significantly lower than other two CO₂ concentration?P<0.05?,but there was no significant difference between ambient and double ambient CO₂ concentration?P>0.05?.The Chryseobacterium of double ambient CO₂ concentration was higher than other two CO₂ concentration treatments,but there was no significant difference between ambient CO₂concentration and intermediate CO₂ concentration?P>0.05?.Then,under ambient CO₂ concentration,we employed the Acinetobacter to do feeding experiment to determine the difference in development time and fecundity between two treatments.Based on two-sex life table analysis,we found that there was no significant difference in the development time,adult longevity,fecundity,population parameters between feeding treatment and blank control?P>0.05?.However,the biological significance of Acinetobacter to N.lugens was still to be studied and verified by molecular biology.