Genetic Structure And Mating System Of Avicennia Marina(Forsk.)Vierh.and Rhizophora Apiculata Bl.in Sanya,Hainan Province,China

The research made a contrastive study of the genetic diversity,genetic differentiation among subpopulations at different ages,mating system,pollen flow,seed flow as well as the fine-scale spatial genetic structure of the population of Avicennia marina and Rhizophora apiculata in Tielugang Nature Reserve by using SSR molecular marker technology,along with the genetic diversity and divergence among the population of A.marina in Yunxiao Nature Reserve.The results are as follows:(1)In Tielugang Nature Reserve,the genetic diversity of R.apiculata(I=1.082,He=0.541)is higher than that of Avicennia marina(I=0.644,He=0.393),and the genetic differentiation among subpopulations at different ages is not significant.The population genetic diversity of A.marina in Tielugang Nature Reserve is significantly higher than that of A.marina in Yunxiao Nature Reserve,and Tielugang is one more haplotype than Yunxiao.There is significant genetic differentiation between the two populations.(2)The mean outcrossing rate of R.apiculata(tm= 1.055±0.111)is higher than that of A.marina(tm=0.742±0.212),and the mean inbreeding rate of R.apiculata(tm-ts=-0.050)is lower than A.marina(tm-ts=0.111),high level of outcrossing rate and low level of inbreeding rate is one of the reasons for the higher genetic diversity of R.apiculata.(3)The mean pollen flow and seed flow of A.marina was greater than that of R.apiculata.By paternity analysis of seeds the distance between the mother tree and the male parent is calculated as pollen flow(88.9 m in A.marina and 34.3 m in R.apiculata).By parentage analysis of seeds the distance between the seedlings and the female parent is calculated as seed flow(37.3 m in A.marina and 20.0 m in R.apiculata).(4)The spatial genetic structure intensity of R.apiculata(Sp=0.072)is slightly higher than that of A.marina(Sp=0.083).The R.apiculata population have a significant spatial genetic structure within a distance of 0 to 12 m,and 0 to 24 m in A.marina.(5)In terms of adaptability,A.marina is more inclined to r strategy of winning by quantity,while R.apiculata is more likely to K strategy of winning by quality.In summary,there are significant differences between A.marina and R.apiculata in Tielugang Nature Reserve in the ecological strategy,mating system,and gene flow(pollen flow and seed flow).As a thermophilic narrow species,R.apiculata'genetic diversity is higher than A.marina as a cold-resistant widely distributed species.It was speculated that R.apiculata,which is in the middle and later stages of succession,is gradually replacing A.marina that in the early stages of succession.