| Orchidaceae is the largest family of flowering plants,with about 736 genera and more than 28,000 species.It widely distributed in various terrestrial ecosystems.It is a highly evolved and specialized family,which makes it one of the hotspots of biological research.It has a complex and unique life history and is sensitive to environmental changes.Many species have high ornamental,medicinal and scientific research value.The whole family is rare and endangered,which is listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora(CITES).The scope of protection is a key area of conservation biology research.Fujian is located on the southeast coast of China and has a good forest vegetation system.It is one of the important distribution centers of orchids.Resource survey is the basic work to understand the orchids diversity of a given region.With the development of molecular biology theory and molecular biology technology,the classification system of Orchidaceae has also undergone corresponding changes.In this study,a special field survey was carried out from September 2012 to March 2018.Meanwhile,based on literature,the species composition,floristic geography,endangered status and systematic taxonomy of orchids in Fujian were also analyzed.Furthermore,Cymbidium ensifolium,a representative orchid species in Fujian was selected as the model,and the systematic research on conservation biology including reproductive ecology,genetic diversity and symbiotic fungi was carried out systematically,which provided theoretical basis for the formulation and implementation of C.ensifolium protection strategy.It also provided reference for other orchids conservation research work.The main research findings are as follows:1.There are 175 species in 78 genera of Orchidaceae in Fujian,including two new species,Bulbophyllum pingnanense J.F.Liu,S.R.Lan&Y.C.Liang and B.yongtaiense J.F.Liu,S.R.Lan&Y.C.Liang.Moreover,three new genera were recorded from Fujian,including Cryptochilus Wallich,Thelasis Blume and Pinalia Lindley.The genera with single species and a few species are dominant,accounting for 88.46%of the total genera.Most of the species distribution is narrow-domain distribution,with strong regionalism.The number of epiphytic orchids in three vegetation areas from south to north showed a gradual decline.The floristic composition is dominated by tropical Asia to tropical Australasia and tropical Asia,and the ratio of tropical to temperate genus(R/T)is 3.1(>1).According to the Chinese Species Red List,IUCN(2017)and Red List of China Higher Plants,the number of threatened species of wild orchids in Fujian is 71,accounting for 39.89%of the total species investigated.The molecular system constructed by the slower-grading chloroplast genes(psaB,rbcL,matK,ycfl)and the nuclear gene Xdh supports the orchids of Fujian were clustered in 5 subfamilies,16 tribes and 14 subtribes.2.The natural population had two flowering periods in 2014 and 2015 and the cultivated population had three flowering periods in 2016 through the observation of the flowering phenology of C.ensifolium.In 2014,the fruit set of two flowering periods of natural population were 18.54%and 10.56%respectively,with significant differences.In 2015,the fruit set of two flowering periods of natural population were 13.55%and 7.81%,respectively,with no significant difference.In 2016,the fruit set of three flowering periods of cultivated population were 31.58%,38.24%and 33.33%,respectively,with no significant difference.Pollen viability and stigma acceptability decreased gradually during the single flower opening period.The breeding system experiments showed that C.ensifloium was self-compatible,and there was no significant difference in the fruit set between self-pollination and cross-pollination.There was no spontaneous self-pollination and apomixis of breeding system of C.ensifloium.There were significant differences in seed vigor and germination rate between self-pollination and cross-pollination,indicating the existence of inbreeding depression of self-pollination.Through observations in natural and cultivated populations,Apis cerana cerana was the only effective pollinator.The characteristics of A.cerana cerana and C.ensifloium are highly matched in functional form.Pollination mechanism is generalized food deception.Flower odor and color plays an important role in the pollination of A.cerana cerana.The size of the inflorescence had no significant effect on the male and female reproductive success of C.ensifloium.There was a significant difference in the fruit set between the single inflorescence and the multi-inflorescence.3.The F values of 21 phenotypic traits were 1.818-18.504 among the ten natural populations of C.ensifloum in Fujian.There were highly significant differences of twenty phenotypic traits,except the length of leaf.The average coefficient of phenotypic variation of 10 populations was 13.67-18.70%.Principal components analysis showed that the rate of cumulative contribution of the 6 principal components was 75.444%,representing the most of the information.The correlation coefficient analysis between phenotypic traits and geographical factors showed that a significant or extremely significant correlation between the 17 traits and geographical factors.The average differentiation coefficient of 21 phenotypic traits was 26.53%,indicating that the variation was mainly within the population.The UPGMA clustering results showed that 10 populations were divided into 3 groups,of which group ? includes Fuzhou,Gutian,Zhouning,Taining,Yongtai,Wuyishan.Group ? includes Yongding and Dehua.Group ? includes Pinghe and Shunchang.The clustering was not according to geographical distance.4.SSR molecular marker analysis based on the distribution of 18 populations of C.ensifolium in Fujian,Guangdong,Guangxi and Hainan showed that 9 pairs of primers detected 118 alleles in the 355 samples.The average of oberserved number of alleles(Na)was 13.1111,the mean effective number of alleles(Ne)was 4.9312,the mean observed heterozygosity(Ho)was 0.2795,the mean expected heterozygosity(He)was 0.7413,and the mean polymorphic information(PIC)was 0.7402.The coefficient of genetic differentiation(Fst)and inbreeding coefficient of C.ensifolium were 0.2945 and 0.4587 respectively.The analysis of variance showed that the genetic variation mainly generated within the population,indicating less genetic information exchange among populations.The results of UPGMA cluster analysis showed that 18 populations were divided into 4 groups,of which group ?only includes Shixing.Group ? includes Shenzhen,Fuzhou,Rongxian,Gongcheng,Hezhou and Changjiang.Group ? includes Taining,Qingliu,Zhouning,Pinghe and Dehua.Group ? includes Yongding,Yongtai,Shunchang,Gutian and Wuyishan.Analysis by Mantel correlation test analysis showed that the genetic distance and geographic distance between different populations were not significantly correlated.5.In order to study the population structure and ecological function of the root-associated fungi of C.ensifolium,the rhizosphere soil and healthy root samples of wild C.ensifolium were collected.The diversity and population difference of rhizosphere and endosphere fungi were estimated by ITS amplification and high-throughput sequencing.The results showed that the rhizosphere fungi belong to 58 genera of 20 classes of 6 phylum,while the endosphere fungi belong to 35 genera of 11 classes of 5 phylum.There was no significant difference in the index of diversity between the two groups.The number of Basidiomycota and Ascomycota were dominant.There was no significant difference between the rhizosphere and endosphere fungi,but the relative was abundance.The ecological function of the dominant root-associated fungi was predicted using FunGuild tool,and there were ectomycorrhizal,wood saprotroph,and arbuscular mycorrhizal.These fungi have the potential to promote C.ensifolium growth. |
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