Genetic Structure And Breeding System Of Kandelia Obovata Populations In Zhangjiangkou Mangrove Forest Of Fujian Province

We study the genetic structure,breeding system,gene flow and spatial genetic structure of the population of Kandelia obovata of pure forest and K.obovata&Avicennia zmarina forest by nine pairs of nSSR primers and three pairs of cpSSR primers in the Zhangjiangkou Mangrove Forestry National Nature Reserve.The results showed that:(1)The two populations were significantly deviated from HWE,and there wereheterozygous deletions,but they did not experience the recent bottleneck effect.The population of K.obovata in pure forest(Na=26.778,He=0.809,I=2.182)and in mixed forest(Na=23.889,He=0.771,I=1.994)had high level genetic diversity,and pure forest was slightly higher than that of mixed forest.There were 21 haplotypes in the population of K obovata in pure forest,which was significantly higher than that of mixed forest(10 haplotypes).Indicating that pure forest did not appear to be genetically negative because of the single species.AMOVE analysis showed that 97%of the genetic differentiation occurred among individuals,and only 3%of the genetic differentiation occurred among different populations.The genetic differentiation of the whole K.obovata population(Fst=0.085)was significant,and the genetic differentiation of pure and mixed forest was also significant.(2)The mean outcrossing rate of K.obovata population was 1.054±0.041(tm)and 1.175±0.170(ts)in pure forest,the mean outcrossing rate of K.obovata population wast 1.321±0.028(tm)andl.350±0.059(ts).There was a high level of outcrossing rate in two populations,and the outcrossing rate of K.obovata in mixed forest was higher than that of pure forest.The mean inbreeding rate(tm-ts)of K.obovata population in pure forest and mixed forest were-0.272?0.011 and-0.001?0.005,respectively.There was no significant deviation from 0,indicating that there was no parental inbreed between K.obovata in pure and mixed forest happening.The high level of outcrossing facilitates high level genetic diversity in high density of K.obovata populations.(3)There were significant differences in the patterns of gene flow(pollen flow and seed flow)between pure and mixed forest.The mean pollen dispersal of pure forest was 9.35±5.51m,mainly concentrated in the 3-6 m.The mean pollen dispersal of mixed forest was 13.88±4.69 m,mainly concentrated in the 18?21 m.The mean propagule dispersal of pure forest was 8.65±7.36 m.The mean propagule dispersal of mixed forest was 9.68 ± 6.32 m.The short-distance dispersal of pollen and propagule may lead to the excess of homozygous.As the distance increases,the propagation frequency of saplings of K.obovata-was not very different in 0-24 m.The results showed that community composition and population density had significant effect on pollen flow and propagule flow.(4)The spatial genetic structure parameters(Sp)of K.obovata were 0.042(pure forest)and 0.054(mixed forest),indicating that there was significant spatial genetic structure.The Fij value decreased gradually with the increase of distance,and there was not difference between the two populations.The genetic relationship of K.obovata was similar to that of the first cousin in the range of 4m.There was not significant spatial genetic structure between saplings of K.obovata in pure foret and mixed forest.According to the hypothesis of spatial genetic structure and patch,neighborhood size of pure forest is 20 m,significantly higher than mixed forest(17 m).In addition,there were significant genetic differentiation among high-density K.obovata forest and K.obovata&A.marina forest at high latitudes in China,but there was no significant difference in genetic diversity among them.Indicating that the difference of community composition is not the main factor affecting the genetic diversity of K obovata,and the biotope and historical evolution may be the main factors influencing the genetic diversity of different communities.However,the breeding system,the gene flow(pollen and propagule propagation mode)of K.obovata were significant difference between the pure forest and the mixed forest.It means that difference of community composition and community density were the main factors affecting them.The minimum protection unit of K.obovata is not less than 20 m and the mixed forest is not less than 17 m when conducting high-density K.obovata population genetic research or determining the size of the protection unit.