【作者】 陈心胜；

【导师】 李庆军；

【作者基本信息】 中国科学院研究生院（西双版纳热带植物园） ， 生态学， 2008， 博士

【摘要】 与东南亚地区连续成片的低地雨林不同,西双版纳的热带植被主要是在温度和降雨量都相对较低的生境中发育。尽管其主要植物科属是热带生态系统成分,但已经到了其分布的北缘。在此生境下,植物的繁殖特征所受到的选择压力可能与赤道地区的热带雨林植物有所不同。此外,植物的繁殖生物学特性也是制定热带雨林保护策略的重要依据。本论文通过大量的野外观察、标本查阅和样方调查,对西双版纳热带雨林植物的性系统和繁殖物候进行了研究,试图揭示性系统进化的生态选择压力和热带季节雨林繁殖物候格局的形成原因,期望为热带雨林的保护提供一定的参考。主要结果如下:性系统在影响植物种群生态和进化的很多方面扮演着关键角色,是热带雨林群落调查的重要目标之一。本文对出现在西双版纳热带雨林42个样方中分别属于109个科、356属的685种植物的性系统进行了全面的研究,并与其它热带生态系统中植物的性系统进行了比较。在这些植物中,60.6%的种类是两性花植物,14.3%的种类为雌雄同株异花植物,另有25.1%的种类为雌雄异株植物。在乔木种类中,雌雄异株成分占到了26.1%,与其它热带地区相似或略高。雌雄同株异花与乔木生活型显著相关并在季节性雨林植被中相对普遍。此外,西双版纳热带雨林中单性花(雌雄异花)的成分显著较高,占所有调查种类的39.4%。这一特征与东南亚热带森林中植物普遍具有小而不显著的花相一致,而这样的花型又与雌雄异花的性系统相关联。植物的繁殖物候受生物因子和非生物环境因子的选择,在热带地区表现得非常多样。多样的繁殖物候主要是由热带植物不同的开花时间、开花频率和花期持续时间塑造的,但我们对这些物候参数变化的重要性却理解甚少。在本研究中,我观察了86种植物的繁殖物候(主要是开花和结果)来检测在热带季节雨林中繁殖物候参数与生态条件及植物繁殖特征之间的关系。在群落水平上,一年之中各个月均有植物在开花,但53.2%的植物在三到五月之间开花,此时正值西双版纳季节雨林的干季末期和湿季初期。植物的开花高峰和干季末期的第一次显著降水(月降雨量超过50 mm)相关,而果实的发育高峰和降雨高峰相吻合,成熟高峰则发生在雨季的末期。在研究期间,降水时间的改变导致了植物开花和果实成熟期的改变。降水可能是影响西双版纳热带季节雨林植物繁殖物候的最重要的气象因子。在西双版纳热带季节雨林中,植物的开花时间和传粉系统显著相关。由多样性昆虫传粉的植物种类倾向于在干季开花,蜂类传粉的植物倾向于在干季末期和雨季初期开花,而鳞翅目昆虫传粉的植物种类倾向于在湿季开花。尽管大多数的植物种类(74%)一年开一次花,但仍有相当比例(22.1%)的植物种类多年开一次花。与新热带的低地热带雨林相比,西双版纳季节雨林中一年开多次花的植物种类较少,并且没有连续开花的植物种类。与东南亚龙脑香林相比较,西双版纳热带季节雨林多年开一次花的植物种类比例较低。大多数植物的花期持续时间比较短,通常不到六个星期。非雌雄异株植物有着比雌雄异株植物显著长的花期持续时间,但由于雌雄异株与一系列的生态条件相关联,要确定雌雄异株的性系统对植物花期持续时间的单独影响,需要进一步的研究工作来比较亲缘关系相近但具有相反性系统的物种。在西双版纳热带雨林中,目前没有证据表明森林片断化和人为干扰对传粉系统造成重大的影响,但大型鸟类和哺乳动物的种群数量降低或灭绝可能会对某些植物种类的种子散布和森林更新带来严重的后果。土地利用方式的改变和原始热带雨林面积的减少,可能会带来区域气候特别是降雨格局的改变,从而影响到热带雨林植物的繁殖物候,甚至可能引起热带雨林植被分布和物种组成的改变。更多还原

【Abstract】 Unlike the seriate lowland rainforests in SE Asia, the tropical vegetation of Xishuangbanna (SW China) has developed in habitats with comparatively lower temperatures and precipitation. Consequently, although most of the families and genera of the flora are components of tropical ecosystems, many have reached their distribution limits in latitude. Selection pressures on reproductive traits in these environments may be different from that experienced in lowland tropical regions. In this thesis, I studied the sexual systems and reproductive phenology of tropical forests in Xishuangbanna by field observations, surveying sample plots, and checking herbaria specimen. Based on these data, I discussed the selective pressures on the evolution of plant sexual systems and the mechanisms underlie the patterns of reproductive phenology.Sexual systems played key role in influencing many components of the ecology and evolution of plant populations. Here, I examine the sexual systems of 685 species of flowering plants belonging to 109 families and 356 genera based on 42 plots and compare our results with surveys of sexual systems from other tropical ecosystems. Among these species, 60.6 percent were hermaphroditic, 14.3 percent were monoecious, and 25.1 percent were dioecious. The percentage of dioecious sexual system among tree species (26.1%) was similar or higher than that of other tropical tree floras. Monoecy was significantly associated with the tree growth form and was relatively common in seasonal forest vegetation. Sexual systems involving unisexual flowers (dicliny) are particularly well represented in the tropical forests of Xishuangbanna accounting for 39.4 percent of all species surveyed. This pattern may be associated with the prevalence of relatively small inconspicuous flowers in the tropical forests of SE Asia and their correlation with diclinous sexual systems generally.Reproductive phenology is determined by the interactions between biotic and abiotic factors and is most diverse in tropical forests. The diversity of reproductive phenology is shaped by variation in timing, frequency, and duration of flowering in tropical plants, yet we have little understanding of the significance of this variation in phenological parameters. In this study, reproductive phenology of 86 species was studied to examine the relationships between phenological characters and ecological traits in a tropical seasonal rain forest. Flowers were available in the community year-round, but 53.2% species flowered in Mar-May corresponding to the late dry and early wet season of the year. At the community level, flowering was temporally associated with rainfall with flowering peak about 2 mo lagged behind rainfall peak. The highest number of species with developing fruits was overlapped with rainfall peak and mature fruits occurred mainly in the late wet season. During the study, the temporal change of rainfall caused the change of flowering and fruiting time. Rainfall may be the key climatic factor in influencing the reproductive phenology of seasonal rain forest in Xishuangbanna.Flowering time (season) was significantly associated with pollinator systems with proportionately more species pollinated by diverse insects flowering in dry season and proportionately more species pollinated by Lepidoptera flowering in wet season. A considerable proportion of species (22.1%) flowered supra-annually although the majority of species (74%) flowered annually. A much lower proportion of species flowered subannually compared with lowland forest in Costa Rica and a lower proportion of species flowered supra-annually compared with dipterocarp forest in SE Asia. Flowering duration of most species was rather brief, usually less than six weeks. Non-dioecious species displayed flowers for a longer period than dioecious species, but this association may be spuriously generated by a suite of ecological correlates with dioecy. Further identification of the exclusive effects of dioecious sexual system on flowering duration should be examined by comparing related species with contrasting sexual systems.Until now, little evidence showed that forest fragmentation and human disturbance caused serious consequences on pollinator systems. However, population decline and extinction of many large birds and animals may impose difficulties on seed dispersal and forest recruitment. The changes in land utilization and deforestation of primary rain forests may bring regional climatic changes especially temporal pattern of rainfall, which may in turn change the reproductive phenology of tropical plants even the distribution and species composition of the tropical forests.更多还原