Adaptive Evolution On Study Of Forsythia Suspensa Based On SCoT Molecular Markers

Understanding the genetic mechanisms of adaptation to environmental variables is a key concern in molecular ecology and evolutionary biology.Determining the adaptive evolutionary direction and evaluating the adaptation status of species can improve our understanding of these mechanisms.F.suspensa is a common dominant species covering the deciduous broad-leaved forest in warm temperate zone of China.It is an ideal material for understanding the evolutionary genetic mechanism of vegetation adaptability in this region.In this study,twenty F.suspensa populations were used as research materials and SCo T molecular marker technique was used as the research method to analyze the genetic structure,detect the EAL,and infer the relationship between environmental variables and adaptive genetic variation.The results are as follows:(1)Ten SCo T primers were selected to investigate the population genetic structure of F.suspensa.A total of 1,242 unambiguous loci were identified with sizes ranging from 60 bp to 1000 bp.The number of loci in 10 primers ranged from 60(SCoT31)to 161(SCoT4).The gene diversity of Nei(H_E)at the species level was 0.124.The lowest number of polymorphic alleles(N_A = 226,PPA = 18.2)was exhibited in SXWT(P1)population and the highest(N_A = 649,PPA = 52.3)in HBDH(P20)population.The lowest gene diversity of Nei(H_E = 0.060)was exhibited in HNSM population and the highest(H_E = 0.223)in HBDH(P20)population.(2)N-J network shows that the twenty populations were subdivided into four genetic groups.Non-hierarchical AMOVA revealed that the significant differences was occurred among these populations(FST = 0.109,P < 0.001).Despite the clear genetic subdivision in the twenty populations of F.suspensa,only minimal genetic variation was occurred among these four groups(5.87%,FCT = 0.059,P < 0.001),and most genetic variations was occurred within the twenty populations(88.01%,FST = 0.120,P < 0.001).Non-significant patterns of isolation-by-distance were detected among the twenty populations of F.suspensa(r = 0.1209,P > 0.05),indicating that geographic distance exerted no significant effect on genetic differentiation.RDA results showed that seven environmental variables were significantly associated with genetic structure,and environmental variables have great influence on the spatial genetic structure of F.suspensa.(3)Using the Baye Scan method,sixty-three outlier loci were identified(5.1% of the total number of SCo T loci).Using the FDIST2 method,a relatively relaxed result of 132 outlier loci(10.6% of the total number of SCo T loci).Based on the results yielded by two identified methods,a total of twenty-six common loci were detected by both methods.Among these outlier loci,twenty-three EAL associated with at least one environmental variable was detected in F.suspensa by using LFMM.Among these detected EAL,twenty were significantly associated with both temperature and precipitation,three were significantly associated with precipitation.The information of F.suspensa EAL have confirmed the hypothesis that ecological habits determine the adaptive evolution of species in many aspects.According to the number of EAL,this study also proposed an evolutionary model for species to adapt to environmental variables.The adaptive evolution status to environmental variables of F.suspensa was studied by this model.