Effects Of Different CO₂ Concentrations On Intraspecific Competition Of Red And Green Pea Aphids

With the sense of crisis brought by atmospheric climate change,it urges scholars to continuously explore and summarize the current situation and rule of its occurrence,making atmospheric climate change becoming a very important research area.This experiment is based on one of these branches.This study used alfalfa variety"Algonquin"as the host plant,and"pea aphid"as the test insect.This study set up three CO₂ concentrations（control concentration 380μL/L,medium concentration 550μL/L and high concentration 750μL/L）and five initial densities（2,4,8,16,32 head/plant（dish））were set,and then investigated the influences of the two factors on the life parameters of pea aphids of the two color types,the effect of intraspecific competition on pea aphid population,effects on feeding behavior of pea aphids of two color types,and the effect on gene expression of symbionts in pea aphids.From the aspects of ecology,physiology and biochemistry to analyze the development trend of pea aphids of two color types in the future climate change.The main research results are as follows:1.Effects of interspecific competition on the population and population growth rate of pea aphid under different CO2 concentrationsUnder the conditions of treatment of three CO₂ concentrations and five population initial densities of pea aphids,after colonization on the plant for 14d and 21d,the results of the population and population growth rate of pea aphids of two color types showed that:At the same initial density,with the increase of CO₂ concentration,the population of pea aphid was severely inhibited;As the same CO₂ concentration,the population growth rate decreases with the increase of the population initial densities of pea aphids,indicating that there has a density restriction effect in population of pea aphid,and the density effect seriously inhibiting the growth of the population.Therefore,it is speculated that the increase of atmospheric CO₂ concentration might inhibit the large-scale outbreak of the two types of pea aphid in the future.2.Effects of different CO2 concentrations and initial densities on the life parameters of pea aphidsAs the same CO₂ concentrations,the populaton initial density had no significant effect on the pre-reproductive periods and post-reproductive periods of red pea aphid,but had significant effect on the reproductive periods,longevity and progeny per aphid of red pea aphid;Under the Medium and high concentrations,the initial density had no significant effect on the pre-reproductive periods,longevity and post-reproductive periods of green pea aphid,but had significant effect on the reproductive periods and progeny per aphid of green pea aphid;The CO₂concentrations had significant effect on the reproductive periods and progeny per aphid of pea aphid;With the increase of CO₂ concentration and initial density,all the life parameters were inhibited,which indicated that the two types of pea aphid had intraspecies competition and density constraints,Furthermore,which would inhibit the large-scale outbreak of the two types of pea aphid in the future climate change.3.Feeding behavior of pea aphids of two color types under different CO2 concentrationsThrough the results of determination of feeding behavior of pea aphids of two color types showed that:Under different CO₂ concentrations,there was no significant influence between the waveform of pea aphid on the explore optimal feeding site of alfalfa leaves and the feeding phloem exudates,which showed that there is no significant effect between the two kinds of pea aphid on the alfalfa surface of the recognition process and the process of feeding alfalfa phloem exudates;However,it has an effect on mechanical disturbance（F wave）of alfalfa when feeding on xylem juice,but there is no significant effect on each other treatment.The G wave of the red type and the green type occurred the maximum value at medium concentration and high concentration,and there has a significant influence between the G wave of the two types pea aphid and feeding the xylem juice.This indicated that different CO₂ concentrations had significant effects on the process of feeding on xylem juice of pea aphids of two different color types.4.Effects of different CO2 concentration conditions on gene expression levels of symbiotic fungi of two color types of pea aphidsThe results showed that the relative expression levels of symbiotic fungi of the two types of pea aphids in each generation treatment occurred the maximum value at medium concentration,and except for the G3 generation,there has significant effects of different CO₂ concentrations on the G1 and G2 generations of the red aphids.There has a significant effect between different generations on the green aphid.Which indicated that long-term living under high concentration of CO₂ will weaken the adaptive capacity of pea aphids to the external environment.