Landscape Genetics Of Opistopopappus Shih

Opistopopappus Shih is a perennial herb of Compositae family,which is only distributed in the Taihang Mountains and has important economic,ornamental and medicinal values.There are two species in this genus:Opisthopappus longilobus and Opishopappus taihangensis.Taihang Mountain’s unique topography and complex climatic conditions should have a significant impact on the species,but this influence has not yet been determined.Using landscape genetics methods,the influence of Taihang Mountain landscape characteristics on the genetic and distribution patterns of Opisthopappus would be explored in this study.Based on transcriptome data,9986 potential microsatellite motifs were found in O.longilobus,among which single nucleotide repeats were the most（43.67%,4322）,followed by trinucleotide repeats（37.31%,3693）and the most abundant repeat motif was ACC/GGT.8194 SSR sites were found in O.taihangensis,with the most single nucleotide repeats（40.32%,3304）;followed by the trinucleotide repeats（39.90%,3269）,the most abundant motif was CTC/CAG.By the detected EST-SSR loci,18,532 primer pairs were designed,160 pairs were randomly synthesized,and 20 pairs of primers that could amplify a bright,clear and single target band were screened for further genetic analysis.Genetic analyses found that:（1）O.longilobus（Na=1.234,Ne=1.323,I=0.276,H=0.201,Hd=0.98667,π=0.013181）and O.taihangensis（Na=1.228,Ne=1.239,I=0.198,H=0.129,Hd=0.99167,π=0.012605）had lower genetic diversity and higher haplotype diversity;（2）PCo A,NJ tree,STRUCTURE,DAPC and SAMOVA analysis all divided the 27populations into two groups（O.longilobus group and O.taihangensis group）.AMOVA and hierarchical AMOVA showed that the variation among populations（58%）was greater than that within populations（42%）,the variation between groups（49%）was greater than between species（19%）and within species（32%）.These results were consistent with genetic differentiation coefficient F_ST=0.593.A total of 132 haplotypes were detected in Opistopopappus Shih populations.There were73 haplotypes in O.longilobus populations and 59 in O.taihangensis populations.All haplotypes were private haplotypes occurred in single population or different species.Low gene flow（Nm=0.0054/0.0043）existed between populations and different species.Spatial autocorrelation analysis showed that an significantly correlation occurred when the populations were within 18-50 km region.There had an obvious genetic barrier between O.longilobus and O.taihangensis.Mantel testing（IBD:r=0.5134,P=0.001;IBE:r=0.3270,P=0.001）and MMRR analysis(r ²_Geo=0.10695,β=0.0013,P=0.001;r²_Env=0.26339,β=0.0016,P=0.001)both indicated that geographical isolation and climatic conditions were significantly related to the genetic variation and diversity of the Opistopopappus Shih populations.Partial Mantel test(r _Geo=0.4218,P=0.001;r _Env=0.0581,P=0.202)and MMRR analysis(β_Geo=0.00152,P=0.001;β_Env=0.00024,P=0.405)also showed that when the geographical distance was constant,the environmental distance was related with genetic distance but not significant.RDA analysis showed that geographic variables can explain more variation.Furthermore,the populations distributed in the northern areas were significant correlated with temperature factors,the populations in the middle and southern areas were significant correlated with rainfall factors.So,the geographical and climatic conditions affected the genetic variation pattern of Opistopopappus Shih.In summary,the genetic differentiation of Opistopopappus Shih populations were affected by the landscape characteristics of Taihang Mountains.Due to geographical isolation and climatic heterogenicity,the connectivity between populations was reduced,population differentiation was promoted,and then adaptive evolution to local climate was occurred in Opistopopappus Shih.