| Camellia azalea Wei, an endemic species, is distributed only in the E'huangzhangprovincial nature reserve of Guangdong which located in Yangchun city, Guangdong province.The resource of C. azalea was severely destroyed after it was found and used. Today, it was anextremely endangered species with the gradual reduction of amount and distribution area. Thepopulation was widely surveyed, and its genetic diversity and genetic structure were studied bymorphological and AFLP and SSR analysis. The population ecology, reproductive biology andplant anatomy were investigated. The phylogenetic relationship of C. azalea was reconstructedby AFLP and cpDNA analysis. Based on these results, The endangered mechanism wererevealed. The results were summarized as follows.1. C. azalea, few individuals in population, was severely destroyed by human. C. azalea isdistributed as narrow bangs along a stream, and its habitat is fragmental. The distributionregion belongs to rainforest climate of tropical northern fringe. The nutrient content of soil islow, lacking P, K element.2. The population structure of C. azalea was spindle types in the natural distributionregion, and the survival curves was Deevey â… type. The population was declining due to lackof seedlings. The population structure difference among the different habitats was definitelydue to the different micro environments. The spatial distribution pattern of C. azaleapopulation was clump distribution, and changed from clump to random with the developmentof population.3. The results of outcrossing index(OCI), pollen-ovule ration(P/O) and pollinationtreatments showed the breeding system of C.azalea is outcrossing type, partly self-compatible,requiring pollinators. The results of determination of wind pollination and observation ofpollination insects showed C. azalea were insects pollination and weak wind pollination.Effective pollinators were bees and butterflies. 4. Natural regeneration of C. azalea was poor with the lack of seeds and seedling in thesoil. With the maturation and natural crack of fruit after2to3months, seeds of C. azaleascattered with gravity. The seed quality of C. azalea was poor, with43.29%full seeds, and thepercentage of full seeds with vitality was35%. Germination rate of seeds was2.05%, and deathrate of seedlings was59.26%in the late.5. The main volatile releasing period of flower of C. azalea were first flowering and fullflowering stage. The main flower parts of volatile releasing were petals and stamens. Diurnalvariation of the main volatile releasing was consistent with the activity patterns of pollinationinsects. The volatile attracts insects and plays an important role in the pollination.6. The flower bud differentiation of C. azalea progressed continually, and the flower budsin different differentiation phases could be observed in the period. The process of flower buddifferentiation was about thirty days, and was divided into six phases: physiologicaldifferentiation, flower primordium differentiation, sepal primordium differentiation, petalprimordium differentiation, stamen and pistil primordium differentiation phases.7.15phenotypic traits of C. azalea population were investigated. The result showedaverage coefficient of variation was25.137%, and9phenotypic traits were significantlydifferent. Variation range of phenotypic traits had large differences among subpopulation.According to AFLP data, expected heterozygosity(He), Shannon's diversity index(I)and thepercentage of polymorphic loci(P) were0.129,0.203and56.760ï¼…, respectively. Geneticvariation among and within subpopulation were24.687%and75.313%, respectively. Geneticdiversity of different age class was not significantly different, and genetic variation among theage class only was1.468%. According to SSR data, expected heterozygosity, Shannon'sdiversity index and observed heterozygosity(Ho) were0.465,0.882and0.303, respectively.Coefficient of genetic differentiation among subpopulation were0.099, and gene flow was2.264. Genetic diversity of different age class had not significant difference, and the same wasdifferent reproductive population. Coefficient of genetic differentiation among the age classwere0.058, and gene flow was4.034. The result of AFLP and SSR analysis showed that thegenetic diversity of C. azalea was low, and that had not significantly different among age class or reproductive population. Genetic differentiation was low, and main genetic variation waswithin subpopulation.Genetic diversity of SSR analysis was higher than that of AFLP.8. The result of morphological, AFLP and cpDNA analysis showed that C. azaleabelonged to an independent branch of the Camellia genus, and the phylogenetic relationshipwas near to Section Camellia with high similarity coefficient.The results showed that the distribution range of C. azalea population is continuouslyreducing, and population is decreasing. Genetic diversity and genetic differentiation of C.azalea population was low, that led to poor adaptability to environment. On the basis of aboveresults, it is suggested that there are three aspects for the endangered mechanisms of C. azalea.(1) Narrow distribution range, habitat fragmentation and hunman disturbance have led to theextinction of a great number of populations, and it is difficult to restore population in shorttime.(2) C. azalea distributes as narrow bangs along a stream. Seeds of C. azalea scatteredwith gravity after fruit maturation and natural crack. Most seeds scattering along the streamwere carried away by the water in the rainy season. With the bad environments and the lack ofsuitable humidity, the seeds were difficult to germinate in the dry season.(3)The seed quality ofC. azalea was poor with shorter fruit ripening, that resulted in poor germination rate of seedsand mass mortality of seedling in the late. For these reasons, C. azalea population severelylacks of seedling, and it is difficult to regenerate the population. |
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