濒危红树植物卵叶海桑的濒危机制及保护策略研究

Sonneratia ovata is seriously threatened and has been ranked as endangered species because of human disturbance, habitat change, narrow distribution range and difficult natural regeneration. At present, research on endangered mechanisms and conservation strategies are absent in Sonneratia ovata. Therefore, it is urgent to carry out scientific research on Sonneratia ovata in order to save the risk of extinction.. Firstly, we are going to study the reproductive characteristics (including the breeding system and pollinating characteristics), reveal mating system and degree of inbreeding depression in terms of phenotype, reveal limiting factors and weak links in reproduction process, and elucidate endangered mechanism and cause. We will use effective experimental means to improve weak links in reproduction process, help them overcome reproductive obstacles to propagate successfully, and release from endangered status.. Secondly, we will study the seeds and seedlings, master optimum conditions of seed germination and seedling formation and effects of different ecological factors on seedling emergence, morphogenesis and seedling growth, reveal obstacles and weak links of seed germination and seedling growth process, and master the relationship among seed germination, seedling growth and environment. We will find appropriate methods to produce more artificial seedlings so as to restore the population number and expand the distribution area.. Thirdly, we will reveal the genetic structure and genetic diversity by SSR and SNP, reveal mating system and degree of inbreeding depression in terms of genotype, and elucidate endangered mechanism and cause in genetics. . Lastly, according to the research results above, we will decide which units are conserved in priority, and formulate conservation strategies and measures. This study will provide scientific base for population restoration, reasonable utilization and effective conservation.

由于人类干扰、生境变化、分布范围狭窄、天然更新困难，卵叶海桑受到严重威胁，被列为濒危种。目前缺少对其濒危机制及保护策略的研究，因此迫切需要对其开展科学研究，以挽救面临灭绝的风险。本项目研究卵叶海桑的生殖特性(繁育系统、传粉特性)，从表型方面揭示交配系统及近交衰退程度，揭示生殖中的限制因素及薄弱环节，阐明濒危的机制和原因。采用有效实验手段完善生殖中的薄弱环节，克服生殖障碍成功完成生殖，脱离濒危。研究种子及幼苗，掌握种子萌发、成苗的最适条件及生态因子对出苗、形态建成和幼苗生长的影响，揭示种子萌发、幼苗生长过程的障碍和薄弱环节，掌握种子萌发、幼苗生长与环境的关系。寻求合适的人工育苗方法恢复种群数量，扩大分布区域。利用SSR和SNP揭示遗传结构及遗传多样性，从基因型方面揭示交配系统及近交衰退程度，阐明濒危的遗传机制和原因。确定保护单元，制定保护策略和措施，为恢复种群、合理利用和有效保护提供科学依据。

卵叶海桑具有抗风、耐贫瘠、耐盐碱等特点，是理想的海防林树种，具有较高的观赏、生态、药用和食用价值。由于人类干扰、生境变化，卵叶海桑受到了严重威胁，自然更新条件恶化，天然更新困难，被列为濒危种。但目前缺少对其濒危机制和保护策略的研究，因此对其开展相关的研究迫在眉睫。.本项目以濒危红树植物卵叶海桑自然居群为研究对象，通过群落生境、生殖特性、种子萌发育苗及保护遗传学等方面的研究，揭示其濒危的机制，并制定种质资源保护策略。主要研究结果如下：① 群落中共有24科49种植物，卵叶海桑居群数量少，分布范围狭窄，林下幼苗极少；② 群落的土壤有机质含量、全钾含量及全氮含量均较适宜，而全磷多处于缺乏状态；③ 单花花期较短，仅有2-4天，花粉活力平均值为83.22-89.35%，柱头可授性持续时间长达4 d；④ 杂交指数、花粉—胚珠比及人工授粉结果表明，交配系统为异交，部分自交亲和，需要传粉者；⑤ 柱头上的花粉萌发、花粉管生长正常，但在胚珠发育过程中，出现了异常现象；⑥ 卵叶海桑林下生境不适宜种子萌发和幼苗生长，萌发率和成活率都很低，制约了该树种的自然更新和居群扩大；⑦ 完整叶绿体基因组是环状双链DNA分子，总长度为153052 bp。利用榄李和拉关木作为为外类群，构建系统进化树，明确了卵叶海桑与近缘种的亲缘关系；⑧ 卵叶海桑的遗传多样性偏低，UPGMA聚类树和主坐标分析 (PCoA) 都将4个居群分为两个遗传组，比较准确反映了居群间的亲缘关系；⑨ SSR结果显示卵叶海桑为混合交配系统类型，以异交为主 (tm = 0.851; ts = 0.676)，存在一定的自交或近交。.针对卵叶海桑的现状及濒危机制，应采取就地保护与自然回归相结合，以就地保护为主，辅之以回归引种，积极进行繁殖，实现在原产地恢复和发展壮大居群，为濒危红树植物的保育提供借鉴。