Genetic diversity and genetic structure of natural populations in an extremely narrowly distributed perennial species Glycine tabacina (Labill.) Benth. on the southeast islands in China

In China, Glycine tabacina (Labill.) Benth. is only distributed in the southeast coast and islands. In this study, 28 natural populations of G. tabacina species were sampled from 13 islands using 22 SSR markers. The Chinese G. tabacina was characterized by higher outcrossing rate and within-population genetic variation, extensive migration, greater population genetic differences and geographically weak-associated genetic differentiation, with higher level of heterogeneity within the natural populations along the southeast islands of China even though this species is a self-pollinating plant. The number of alleles per locus averaged 5.77 and ranged from 2 to 16. The expected heterozygosity (H-e) per locus averaged a value of 0.51, varying from 0.08 to 0.80. As an autogamous species, the Chinese G. tabacina unexpectedly showed a relatively high mean outcrossing rate in single locus (t(s)=6.52%) and multilocus (t(m)=6.75%), higher mean gene flow (N-m=0.315), lower mean gene differentiation index (G(st)=0.436), and particularly, relatively lower among-population genetic variation (43.55%) and higher within-population genetic variation (49.66%) revealed by analysis of molecular variance. Spatial autocorrelation analysis revealed that populations within a radius of approximately 14.7km would have a positive and significant genetic relationship to one another. However, the event of long-distance genetic background dispersal was revealed by individual assignment test and haplotype analysis (>200km dispersal was inferred, but >56km dispersal was observed). The north and middle-north islands of Fujian Province seemed to be the center of genetic diversity.