Study On The Population Genetic Structure And Diffusion Mechanism Of Sycamore Lace Bug,Corythucha Ciliata(Say)

Sycamore lace bug,Corythucha ciliata(Say)(Hemiptera:Tingidae),native to temperate areas of the Middle East of the United States,mainly harms Platanus plant.It has the characteristics of rapid spread and serious damages,and can break out in the new habitat for a short time.As a result,it is difficult to effectively control for sycamore lace bug.Since invasion into China,sycamore lace bug has rapidly spread to many areas in China where the Platanus plant is cultivated.However,the diffusion mode and route of the plant in China are still unclear.However,there are still unclear about spreading mode and route of the invasive exotic pest in China.In this study,the genetic structure of 12 geographic population of C.ciliata(Changsha,Wuhan,Shanghai,Beijing,Shijiazhuang,Jinan,Taiyuan,Hangzhou,Chengdu,Chongqing,Guiyang,and Zhengzhou)were analyzed based on COI gene,the flight ability and short-distance diffusion ability of sycamore lace bug were tested by flight mill system and phosphor labeling-release-recovery method,and the diffusion path of C.ciliata in China was also simulated by HYSPLIT trajectory analysis model.Based on those results,the transmission path of C.ciliata found out in China.These findings provide the biological basis and decision support for the forestry department to formulate the control measures of C.ciliata.It is of great significance to effectively control the spread and harm of C.ciliata in China.The main conclusions are as follows:(1)Through PCR amplification and sequencing,nine haplotypes were found in twelve geographical populations of C.ciliata,four of which were exclusive haplotypes and account for 44.44% of all haplotypes.The existence of four exclusive haplotypes from C.ciliata indicates that genetic differentiation has taken place among different populations of C.ciliata.The H1 was ancestorhaplotype has deduced by establishing haplotype network map.Genetic diversity analysis within the population showed that there were no polymorphisms in the Changsha and the Shanghaipopulations,and the remaining populations were highly polymorphic.The average Hd,?,and k values of these populations were 0.584,0.00299,and 2.276,respectively.Guiyang,Chongqing and Beijingpopulations have the higher genetic diversity,while Wuhan populations have lower genetic diversity.Population phylogenetic tree showed that Changsha,Shanghai,and Wuhan populations have the closest genetic distance to European populations such as Germany.Therefore,we speculated that Changsha populations of C.ciliata may have been invaded from European populations and then began to spread to other regions in China.The analyzation of molecular variation analysis(AMOVA)was divided into four groups based on the result of population phylogenetic tree above mentioned.AMOVA analysis of 12 populations of C.ciliata showed that inter-group variation accounted for 26.03%,intra-group variation accounted for 21.78%,and intra-group variation accounted for 52.19% of the total variation.Therefore,the main source of genetic variation among twelve populations of C.ciliata was intra-individual variationin China.(2)Genetic relationship between different geographic populations mainly analyzed the genetic differentiation coefficient(FST value)and gene flow(Nm value)to judge the distance of genetic relationships and the frequency of gene exchange between 4 groups and between 12 geographic populations.The results showed that Huazhong groups and Huadong groups are lowly differentiated,while Huazhong groups was extremely differentiated from the Xinan and Huabei Groups.Meanwhile,Huadong Groups are also highly differentiated from Xinan and Huabei Groups.FST values of Changsha,Shanghai,and Wuhan populations are 0,indicating that there is no genetic differentiation or low genetic differentiation among the three populations.FST value was all 0.8868 between Shanghai and Taiyuan populations and between Changsha and Taiyuan populations,indicating that there is a high degree of genetic differentiation between the two groups of populations.The results of Mantal correlation test showed that the genetic differentiation among 12 geographical populations was not caused by geographical distance,and there was no distance isolation between different populations.There was nosignificant correlation between between haploid diversity of sampling sites and longitude and latitude of sampling sites in 12 geographic populations.The results of population history analysis and effective mobility analysis of the four groups showed that the Huazhong group underwent population expansion,while the other three groups did not.It is speculated that the migration and entry routes of 12 geographic populations were as follows: the migration route of the insect to the east,in turn,was Changsha,Wuhan,Shanghai and Hangzhou;the migration route to the southwest,in turn,was Changsha,Guiyang,Chongqing and Chengdu;the migration route to the north,in turn,was Changsha,Wuhan and Zhengzhou,and eventually arrive to Beijing through two routes(One start from Taiyuan to Beijing,and the other start from Shijiazhuang,reached Beijing via Jinan).(3)The flight ability of Male and female C.ciliata at age old and differern temperatures were tested using the insect flight mill system.These results showed that the average flight distance and average flight time of C.ciliata adults first increased with the increase of age,reached the maximum at 10-day-old,and then decreased gradually.The average flight distance and flight time of 10-day-old adults within 24 hours were 1361.75 m and 4580.36 s,respectively.However,there was no significant difference in flight speed among different ages of adults.Under different temperatures,the longest flying distance and flying time of tenday old adults were 1160.53 m and 6518.92 s in 25?,respectively,while the maximum flight speed was 0.25 m/s at 28?.The flight ability test between the female and the male adults showed that the average flight distance(t= 2.191,df= 141,P=0.03)and average flight time(t= 2.919,df= 141,P=0.004)of female adults were significantly higher than that of male adults,while the average flight speed of male adults was significantly higher than that of female adults(t=2.014,df=141,P=0.04).(4)The label-release-recovery method was used to measure the ability of the short-range diffusion of C.ciliata in different seasons.In the summer,the amount of recycling insects in the west and north directions was relatively large,and the number of recycling insects in the east and south directions was low.In terms of diffusion distance,the westward location was the farthest at 190.9m,followed by the northward.The average diffusion distance in the west and north direction was significantly higher than the east and south directions.The average diffusion distance in all four directions gradually increased with the increase of release time,reached the peak on the 10 th day,and then gradually decreased.In the autumn,the number of recovered adults in the westerly site was the largest,and was gradually decreasing in the north,east and south.In terms of diffusion distance,the westward diffusion was the farthest at 254.6m,following the northward and southward.They were significantly higher than the eastward location in average diffusion distance(180.2m).The average diffusion distance in all four directions firstly increased with the release time,peak around the 10 th day,and then gradually decreased,similar to summer.The number of recovered adults and average diffusion distances in autumn were significantly higher than in summer.Sycamore lace bug have a certain short-distance diffusion ability in the wild,which was affected by many factors such as inter-species competition and natural wind.(5)The emigration and immigration paths of C.ciliata in Changsha,Wuhan,Shanghai,Hangzhou,Guiyang,Chongqing,Chengdu,Wuhan,Zhengzhou,Taiyuan,Jinan,Shijiazhuang and Beijing were simulated using the HYSPLIT model,and the population diffusion paths of C.ciliata in China were simulated based on the genetic structure analysis of different geographical populations.The migration and diffusion trajectories of Sycamore lace bug in China were speculated.The main distribution area of C.ciliata was in Changsha,where it was the source of insects.The insect diffuses eastward to Wuhan,Shanghai,Hangzhou,Changsha,Guiyang,Chongqing and Chengdu;southward to Guiyang,Chongqing and Chengdu;northward to Zhengzhou,and the insect ultimately arrived in Beijing through two routes: Zhengzhou?Taiyuan?Beijing and Zhengzhou?Shijiazhuang?Jinan?Beijing.This study found that the bug could spread farther with the airflow within 24 hours,and spread over thousands of kilometers within a few days.Based on a simulated route for successive departures,it took only 4 days from Zhengzhou to Zhangjiakou.In this paper,using the methods of insect behavior,such as flight ability test,short-range diffusion ability test,airflow diffusion trajectory simulation and using molecular biology methods based on mitochondrial COI gene,we analyzed the genetic structure of the population of the bugs in main distribution areas from China and simulated the spreading path of C.ciliata in China.Further,the spreading mechanism of the insect in China was found out.The dissemination mechanism provides theoretical support for the prediction of the spreading trend and route of the invasive pests in China,as well as for the scientific prevention,control and management of the invasive biological problems.