Population Structure Changes Over Time And Rapid Differentiation Mechanism Of Hyphantria Cunea In China

Hyphantria cunea is an important invasive pest with biological characteristics such as wide range of hosts,strong reproductive capacity and strong environmental adaptability.It has caused serious damage to agriculture and forestry and its distributions are increasing in China in recent years.It was found in previous study that Hyphantria cunea had differentiated into two groups during the process of dispersal in China.Studying the genetic structure change of Hyphantria cunea during its dispersal andthe influence factors could provide new ideas to reveal the adaptive mechanism of pests to the new environment and establish reasonable quarantine and prevention measures.In this study,microsatellite markers were used to analyze the genetic diversity and genetic structure of Hyphantria cunea populations in same localities at different years.The differentiation degree of new invasivepopulations and its invasion source will be revealed.Moreover,the genetic stability of Hyphantria cunea populations in the original invasivearea and the influence factors of the rapid differentiation of Hyphantria cunea will be clarified.The main results were as follows:The results with literature research suggestes that the dispersal speed of western group was faster than eastern group.The genetic diversity and genetic structure of six Hyphantria cunea populations in the regional invasiveareas at different years were analyzed based on microsatellite markers.There was no significant difference in allelic richness among populations in same localities at different period by Wilcoxon rank sum test and Hyphantria cunea could maintain genetic diversity.The result of Wilcoxon rank test indicates that the Fsr of Hyphantria cunea populations at different periods were not significant different.The genetic structure of Hyphantria cunea populations in the original invasiveareas did not differentiate at different years.However,the genetic differentiation between eastern group and western group increased.The results of phylogenetic tree and Structure clustering suggestes that the genetic structure of Hyphantria cunea populations in same localities at different years did not change significantly.Although principal component discriminant analysis indicates that the genetic structure of Hyphantria cunea populations in same localities at different years had a certain degree of genetic differentiation.In summary,Hyphantria cunea populations in the original invasiveareas were able to maintain the genetic structure during the study.The genetic diversity of Hyphantria cunea populations was analyzed based on microsatellite markers.The results suggestes that the allele richness of marginal populations in the new invasiveareas was higher than eastern group or western group.Structure cluster analysis indicates that sixteen populations were divided into three groups.Marginal populations of Hyphantria cunea had an obvious genetic differentiation and have differentiated into a new group.The results of Fsr,phylogenetic tree,DAPC and TESS analyses suggested that marginal populations were differentiated from western group.The effects of geographical isolation and climatic variables on the population genetic structure of Hyphantria cune and the mechanism of its genetic differentiation were analyzed based on microsatellite data.It was found that gene flow mainly exists within groups and the gene flow among the groups were restricted to varying degrees through gene flow analysis.Moreover,gene flow between groups were decreased at different years.IBD test indicates that the correlation between genetic distance and geographical distance was significant(r=0.6708,P<0.001).The results of RDA suggestes that the interaction of geographical distance and climatic variables was provided more contribution to genetic variation of Hyphantria cune populations than either of them.In summary,the genetic diversity and genetic structure of Hyphantria cunea in the original invasiveareas remained relatively stable.Under the combined action of vast geographical space and complex climatic conditions,marginal populations rapidly differentiated when spread to new areas and gradually formed more complex genetic structure and higher genetic diversity.