Fig. 3

Likely genetic clusters and geographical barriers existing among 22 populations of Sonneratia. alba. a Bayesian clustering analysis of the seven nuclear genes for 22 populations of S. alba using STRUCTURE. To show the hierarchical population structure across the IWP region, in addition to the optimal clustering of K =3, the clusterings under K = 2 and K = 4 were also given. b Putative geographical barriers identified within the IWP regions. The red line represents detected barriers and the thickness corresponds to the number of genes that support this barrier. The bars showed the result of Bayesian clustering analysis when K = 3. Population abbreviations were defined in Table 1