3.4 Genetic differentiation and distance of populations
The genetic differentiation analyses based on 43 populations of P. villosa revealed that the total gene diversity (H t) was 0.2052, the average gene diversity within populations (H s) was 0.1088, the genetic differentiation between populations (G ST) was 0.4689, and the gene flow (N m) was 0.5761. The value of N m indicated that a limited level of gene exchange existed within the species (Table 3). With respect to populations of Group 1, the values of H t, H s andG ST were 0.1668, 0.1102, and 0.3402, respectively, while these were 0.1918, 0.1083, and 0.4349 for Group 2. Thus, the genetic diversity of Group 1 was lower than that of Group 2, and the genetic differentiation was smaller. The gene flow among populations within Group 1 and Group 2 was 0.9996 and 0.6605, respectively, which revealed that the gene exchange among populations within Group 1 was more frequent.