| Atractomorpha species are important leaf-eating pest of crops distributed across 20provinces(autonomous regions)in China.Nymphs and adults feed on the leaves of various dicotyledonous crops.Over the past decades,Atractomorpha insects have been recognized as secondary phytophagous pests in China,but little attention has been paid to their occurrence and damage area.In recent years,the occurrence range and damage area of these pests have expanded,and members of the genus have become the main pests of certain crops in some areas.Environmental temperature is an important ecological factor,affects their growth,reproduction,and distribution.Few researchers focus on morphological or genetic differentiation of different geographical populations of Atractomorpha species or the iradaptability to different temperatures.Understanding how pests adapt to temperature is important in predicting their future distribution range and possible impact.In order to further explore the above problems,this study investigated the distribution of Atractomorpha insects in farmland in China and performed floristic analysis to identify their preferred crops.Atractomorpha sinensis was identified as the dominant species of pest locusts.The morphological,biological,ecological,and genetic differentiation of different geographical populations of A.sinensis were studied from the perspective of environmental temperature adaptability.The correlation between environmental temperature range and population biological and ecological parameters was analyzed,and the associated physiological and biochemical mechanisms and related genes were investigated.This work provides a theoretical basis for explaining how different insect populations respond to climate change,which can be used to predict pest population dynamics for better prevention and control.The main results are as follows:1.Through a national farmland survey and floristic analysis of Atractomorpha species,A.sinensis was identified as the dominant pest species,and its known distribution area in China.2.The relationships among 13 geographical populations of A.sinensis were studied by numerical cluster analysis of 54 morphological characteristics.R-type clustering showed that the bridge width of the male dorsal horn was highly correlated with the length-width ratio of the male dorsal horn and the distance between the medial horns.There were also correlations between hind-foot internode length,hind anterior wing length,and compound eye spacing.The Q-type clustering results showed that the hierarchical combination line L3(D=6)is divided into six branches.Among them,Guangzhou,Qujing and Yan’ an populations were clustered into one single branch.3.R-type clustering of biological and ecological characteristics of six populations from different morphological branches showed that biological parameters clustered into groups according to the same temperature.Q-type clustering of six geographical populations divided them into three branches: The first branch included the Chengdu and Guangzhou populations;the second branch included the Jinan,Zhengzhou,and Yan’an populations;and the third consisted of the Qujing population.These clustering results are similar to the morphological differentiation results.4.Seeing from mitochondrial genes,the genetic differentiation of 13 geographical populations of A.sinensis in China were analyzed.The total population haplotype diversity was relatively high,the level of gene exchange within the populations was low,and overall genetic differentiation was large.The populations of Qujing,Yan’an,and Guangzhou had obvious genetic structure variation compared to other populations.Mantel tests detected a positive correlation between the geographical distance and genetic distance of various groups,indicating that the Chinese A.sinensis population did not expand recently.These results suggest that geographical isolation was the main factor causing the differentiation between the geographical populations of this pest.5.Analyzed the adaptability of A.sinensis populations to the difference of habitat environmental temperatures.The results showed that the adaptation to lower environmental temperature is manifested in that the generational development period(developmental rate)of high-latitude populations were significantly shorter(higher)than those of low latitude populations at lower ambient temperature,and vice versa at high environmental temperature.The fecundity per female,population trend index,and net reproductive rate of different geographical populations were generally the highest at 24°C.Therefore,24°C is the most suitable ambient temperature for the life activities of geographical populations,and is most conducive to the growth of the next generation.In the natural environment,A.sinensis population adapts to the high temperature area(low latitude)by increasing the development starting temperature,the generation developmental rate and the intrinsic rate of increase,reducing the effective accumulated temperature,the mean generation time and the population trend index,and vice versa to the low temperature area(high latitude)adaptation.6.The physiological mechanisms of geographical population of A.sinensis adapting to environmental temperatures were further analyzed.The supercooling point and the accumulation of cold-resistant substances in the bodies of insects from low latitude populations were proportional to the temperature and were higher than those in high latitude populations,but the cold resistance was weak.However,the cold tolerance of the Qujing population at low latitudes and high altitudes showed a reverse trend.While adapting to high ambient temperatures,the accumulation of stress-resistant substances increased,and the activity of antioxidant enzymes increased to resist transitional high temperatures.If the temperature exceeded the optimum,heat resistance decreased continuously until death.Generally,except for the Qujing population,the heat resistance of low latitude populations was stronger than that of high latitude populations,and the heat resistance of females was stronger.The above results provide a scientific basis for predicting the population dynamics and formulating control measures in different regions.7.Via the high-throughput transcriptome sequencing technology,genes related to adults’ adaptation to environmental temperature were analyzed.A total of 232990 unigenes with annotated information were obtained by sequencing,splicing and assembly,including 7674 differentially expressed genes.The up-regulated genes in females were more than those in males.Under high temperature stress,adult differentially expressed genes were mainly involved in carbon metabolism,endoplasmic reticulum protein processing,oxidative phosphorylation,longevity regulating pathway-multiple species,antigen processing and presentation,biosynthesis of amino acids,PI3K-Akt signaling pathway,plant pathogen interaction,estrogen signaling pathway,etc.,from which 45 heat shock protein genes were selected from male and female adults(mainly Hsp90 and Hsp70),which were significantly enriched in oxidative phosphorylation,endoplasmic reticulum protein processing and life regulation pathway-multispecies.The results lay the foundation of molecular resources for temperature adaptability and related gene mining and bioinformatics analysis of other insect states of A.sinensis. |
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