Effects Of Road Corridors On The Genomic Structure Of Ageratina Adenophora Populations

Ageratina adenophora(crofton weed),is a worldwide noxious weed.It invaded southern part of Yunnan Province,China,from Myanmar in the 1940s,and was widely distributed in southwestern China.The corridor effect of roads promoted the rapid spread of A.adenophora along the roadside,leading to serious ecological damages on local ecosystems.In this paper,we sampled along the roadside of the Burma Road and 213 State Road in Yunnan,and in adhere areas with Myanmar,Guizhou,Guangxi,Sichuan.We analysed 39 A.adenophora populations by RAD-seq to reveal the influence of road corridors on its population genomic structure,as well as its population establishmental process.The results were summarized as follows(1)Road density and connectivity in Yunnan Province was low.The area without roads or with low road density was accounted for 83.3%of the total area of Yunnan.Road network pattern in Yunnan was typically unequal.The road density in the central and eastern regions was higher than that in the western and southern regions.Kunming,Qujing,and Yuxi had the highest road density(2)By nuclear DNA genome sequencing of 181 individuals in 39 A.adenophora populations,a total of 125.88 million sequences(MReads)were obtained,in which 264,375 SNPs were found.The statistical analysis of population genetic diversity showed that the average percentage of polymorphic loci(PPB)was 64.56%(52.17%?68.46%),the expected heterozygosity(He),average allele frequency(P),and nucleotide diversity(PI)were respectively 0.2564,0.7855,and 0.2958.The genetic diversity was significantly negatively correlated with longitude and road density.(3)The coefficient of genetic differentiation among populations(FST)and gene flow(Nm)were 0.0397 and 6.16,and the coefficient of genetic differentiation within populations(FIS)was-0.24.The genetic differentiation among populations was small and gene flow was strong Genetic relationship among the populations analyzed by PCA and Admixture showed that there were no significant spatial genetic structure.By Mantel test,it was indicated that genetic differentiation had no significant correlation with geographical distance.The road corridor promoted the spreading of the A.adenophora populations along the road,and reduced genetic differentiation among populations caused by distance isolation.Landscape connectivity overwhelmed isolation by distance.