Population Dynamics And Scutel Color Variations Of Bactrocera Dorsalis (Diptera: Tephritidae) In Jiangxi And Fujian Regions

Bactrocera dorsalis(Hendel)is a major invasive pest in the world.In the last century,B.dorsalis invaded Jiangxi and Fujian and had a significant impact on fruit and vegetable crops in the invasive areas.In the paper,we studied the life history and population dynamics of B.dorsalis in Jiangxi and Fujian,and analyzed the effects of environmental factors on the population dynamics of B.dorsalis.In the process of field monitoring,it was found that there were yellow,yellow-white and white differentiation in the color of scutel of B.dorsalis.The bioinformatics analysis of individuals with different color of scutel was conducted by resequencing method,which indicated that they were still the same species.The results are as follows:(1)In the natural environment of Nanchang,Jiangxi Province,the results of indoor rearing and outdoor investigation showed that there were 4-5 generations of B.dorsalis a year in Nanchang,Jiangxi Province,overwintering with pupae.The adults of B.dorsalis first appeared in early May,the density was low in June,the population density began to rise in July,and there was an obvious density peak between late August and early November,and then the density decreased.The adults could not be detected in late December.The population of B.dorsalis in Nanchang area showed a decreasing trend from2017 to 2022.In the monitoring area,monthly mean temperature,monthly mean high temperature,monthly minimum temperature and monthly rainfall were the key factors affecting the population density of B.dorsalis.(2)We found that the posterior pectoralis of B.dorsalis adults from Fujian region had different colors in the survey,namely yellow,yellow-white and white.The color of scutel of B.dorsalis adults trapped in Nanchang were all yellow,while the B.dorsalis adults trapped in Fujian were differentiated in the color of scutel.60% of the adults were yellow-white,11% were yellow,and 28% were white.In order to clarify the differences of biological characteristics among individuals with different colors of scutel,the oviposition selectivity,hatching rate,pupation rate,eclosion rate,adult lifespan,single female oviposition,ratio of female to male and survival rate of overwintering were determined in the laboratory.The results showed that there were no significant differences among those individiuals with yellow,yellow-white and white scutel in the hatching rate,pupation rate,eclosion rate,adult life span and the ratio of female to male,while the single female spawning capacity and overwintering survival rate of B.dorsalis individuals with yellow scutel were significantly higher than those of yellow-white and white ones.(3)In order to further clarify the color differentiation among B.dorsalis individuals with coloured scutel,8 samples were selected for DNA resequencing from yellow,yellow-white and white individuals.A total of 90.05 G of bioinformatics data was obtained,with an average sequencing depth of 10.14 X and an average coverage depth of 90.65% for reference genes.A total of 1,912,256 SNPS and 4,253,409 In Del were obtained by population variation detection.Cluster analysis showed that the yellow,yellow-white and white flies clustered into one group,and PCA analysis also showed that there was close genes exchange among the groups with color differentiation in the scutel of B.dorsalis.The selective clearance analysis showed 434 differentially expressed genes in yellow group vs yellow white group,430 in yellow group vs white group,and 254 in yellow group vs white group.Cluster analysis of these differentially expressed genes showed that individuals with yellow scutel had significant differences in environmental information processing,metabolism and some KEGG pathways of genetic information processes compared with those individuals with yellow-white and white scutellum,and the epigenetic characters of scutellum color of B.dorsalis might be related to these differentially expressed genes.Integrated analysis implied that the individuals with different colors of scutel are still the same species though the color of their scutel is differentiated into yellow,yellow-white and white by the biological characteristics and molecular biology research.The results are great significance for further study on the morphological differences,occurrence characteristics and control techniques of different geographical populations of B.dorsalis.