石栎属两种果实包被类型物理化学防御权衡与生殖能量投入研究

There are two types of fruit of Lithocarpus, acorn and enclosed receptacle (ER) fruit. Acorn fruit is similar to the temperate oak's acorn, the seed is mainly surrounded by the thin exocarp tissue. In an ER fruit, the exocarp tissue is shortened,while the receptacle tissue of ER fruit is extremely elongated and lignified, becomes the main tissue covers the seed. The applicant's previous study revealed a trade-off system between the mechanical and chemical protection of acorn and ER seeds: as receptacle represents strong mechanical defense for ER seeds, there is high level of macronutrients in the seeds; On the toher hand, acorn seeds lack of mechanical protection due to the weak husk,so to prevent predation, there is high level of antifeedants, especially fibers, in acorn seeds.But due to sampling problems, lacking of husk mechanical analysis, as well as using seed size to represent reproductive energy, this study lacked of support from the analytical methods. To compensate these three problems, I propose to first, analyse the difference in fruit reproductive energy investment level,to test the hypothesis that compared to acorn fruits, ER fruits has greater reproductive energy investment. Secondly, by quantifying the chracteristics of fruit mechanical protection, and combining with the seed chemical analysis, reveal the fruit mechanical and seed chemical trade-off mechanism betwwen acorn and ER fruits, as well as uncovering the evolutionary force behind the mechanism. Meanwhile, test the hypothesis that instead of tannins, fibers are a group of antifeedants that is more important in chemical defense for Lithocarpus seeds.This study will not only provide the background to understand the speciation and diversity of Lithocarpus in the Hengduan Mountains region, but also assist researchers to review the complex taxonomy and phylogeny problems of Fagaceae from a new perspective.

石栎属有两种果实包被类型，橡实和花托包被实。该项目申请人此前的研究发现其物理化学防御权衡机制：因木质化加厚的花托代表强物理防御，所以花托包被实种子内富含常量营养元素；而橡实种子由单薄外果皮包被，因此种子富含拒食素，尤其是纤维素，抑制捕食者对种子的消费。但由于采样不足，缺乏果实物理防御特性分析，以及生殖能量投入测定不准确的问题，该研究对结论的支持力度不足。针对这三方面不足，该申请项目拟通过首先分析两种包被类型果实在生殖能量投入，来检验花托包被实生殖能量投入较橡实更大这一假说。其次，通过量化果实物理防御特性并与种子化学成分分析相结合，解析橡实与花托包被实在捕食压力下形成的物理化学防御权衡机制及其进化驱动力。同时，验证橡实种子中拒食素中的纤维素成分，是较单宁更重要化学防御成分这一论点。此项研究为了解横断山脉石栎属的物种多样性及其分化奠定了理论基础，并为理解壳斗科复杂系统发育问题提供了突点。

作为壳斗科的第二大属，超过300余种的石栎属（Lithocarpus）植物是中国和东南亚地区热带和亚热带森林中的重要生态组成成分。通过对石栎属两种果实包被类型，橡实（AC）和花托包被实（ER）的果实形态、果实发育、物理防御和地理分布四方面研究的开展，我们发现虽然橡实是更常见和普遍的果实类型，但是两种果实类型通常混生于不同区域的不同森林类型，且它们共享中国南部和东南亚两个地理分布中心。结合此前的研究，我们发现了两种果实类型的果实形态和物理化学防御权衡：橡实（AC）的种子主要被果皮包被，代表弱机械防御，因此种子内富含化学防御成分；花托包被实（ER）种子被木质化加厚的花托包被，代表强物理防御，种子内复航敞亮营养元素成分。但是两种果实类型在果实发育初期的形态和结构类似，果实各部分组织分化顺序也类似，而橡实和花托包被实分别以显著的内果皮和花托的发育分化为标志，成为两种果实类型成熟状态时的形态区别的主要原因。壳斗作为保护发育中果实的结构，对于橡实类型的保护程度更为显著。该研究从果实特征和发育方面阐明了两种果实类型的同异，成为石栎属果实类型的进化研究的重要铺垫。