Abstract: Taking two natural populations of Phoebe bournei of different sizes in Fujian Province (Jian’ou and Shunchang) as the research objects, we used 16 pairs of SSR primers to genotype 78 parents and 480 offspring from 16 parents, and estimated the mating system parameters of the offspring and the genetic diversity parameters of the parents and offspring. The results showed that the genetic diversity of the offspring population (H_e=0.71) was slightly lower than that of the parents (H_e=0.80), but the difference was not significant, indicating stable genetic diversity. The average observed heterozygosity of both the offspring and parent populations was higher than the expected heterozygosity, indicating that offspring and parent populations were primarily heterozygous. There was a high outcrossing rate (t_m=1.200) and a low level of biparental inbreeding (t_m-t_s=0.195) in P. bournei. The biparental inbreeding coefficient was higher in the larger Shunchang population (0.209) than in the smaller Jian’ou population (0.089), while partial kinship was observed among pollen donors in the Shunchang population. Overall, there was no kinship between pollen donors in the two populations (r_p(s)-r_p(m)=-0.051), and the effective number of pollen donors was low (N_ep=1.40). In conclusion, the offspring of P. bournei natural populations largely maintained high genetic diversity of the parents. The natural populations of P. bournei had a high outcrossing rate, with localized inbreeding within populations and low inbreeding level. Current habitat fragmentation had not yet severely negatively impacted the mating system of P. bournei. It was recommended to reduce human disturbance and habitat destruction, maintain the natural regeneration capacity of populations, promote pollen dispersal among subpopulations, and reduce the effects of genetic drift.

Key words: Phoebe bournei, natural population, mating system, genetic diversity, SSR