中国云杉属 (Picea)物种亲缘关系和性状分化的环境驱动机制

Spruces (Picea) in China can be grouped into three sections, i.e. sect. Picea, sect. Casicta and sect. Omorica, according to their morphological characteristics. Alternatively, they can be classified into phylogenetically distinct clades. Spruce species within a section, however, are not necessarily more similar in terms of their phylogenetical relationship than those between sections, which suggests a significant morphological parallel evolution among spruces. However, it remains uncertain with respect to the issue such that whether morphological and phylogenetical divergence among spruces are subject to different selective pressures. Meanwhile, as important morphological traits used for spruce classification, leaf traits are supposed to carry strong climatic signals yet little is known about the ecophysiological mechanism underlying the observed morphometric variation. This project would plan to answer the questions as mentioned above by examining the difference of climatic condition among different sections and different clades to reveal the key selective pressures that account for their divergences. In addition, we would measure leaf functional traits such as carbon isotope ratio (δ13C), leaf nitrogen, phosphorus, leaf specific area and leaf dry matter content for 16 spruce species as surrogates of plant physiological traits. We attempt to disclose the ecophysiological mechanism underlying the observed morphometric variation. The findings of this project would offer a theoretical base for the practice of spruce breeding and vegetation restoration in subalpine area.

云杉属 (Picea)地理分布与环境关系的研究已经积累了许多成果，但云杉物种亲缘关系和性状分化的环境驱动机制尚无明确解答。根据针叶横截面和气孔形态，中国云杉属物种可划分为云杉组 (sect. Picea)、丽江云杉组 (sect. Casicta)和鱼鳞云杉组 (sect. Omorica)；根据物种间的亲缘关系，又可划分为两个分支 (Clade-1, Clade-2)。然而，形态组与亲缘分支在物种组成上并无对应关系，说明云杉的性状变异存在平行进化现象。据此假设：云杉物种亲缘关系和性状分化可能遵从于不同的环境梯度。本项目拟在资料集成和野外调查的基础上，弄清中国云杉植物的环境背景，测定针叶形态性状、碳稳定性同位素比率和氮磷含量等功能性状，分别构建基于基因测序和性状资料的物种分化谱系树，研究物种亲缘关系和性状分化与环境因子间的关系、以及植物形态性状所表征的功能意义，验证本项目的科学假设。

云杉属地理分布与环境关系的研究已经积累了许多成果，但云杉物种亲缘关系和性状分化的环境驱动机制尚无明确解答。云杉属物种可划分为云杉组、丽江云杉组和鱼鳞云杉组；根据物种间的亲缘关系，又可划分为两个分支。云杉物种亲缘关系和性状分化是否遵从于不同的环境压力？我们测定云杉针叶性状，分别构建基于基因测序和性状资料的物种分化谱系树，研究了物种亲缘关系和性状分化与环境因子间的关系，得出了如下结论：. 中国云杉林的地理分布与经纬度和气候因子密切相关，地理位置是中国云杉林物种组成分异的主要驱动因素，湿度是中国云杉属各形态组间分异的决定因子，而云杉属系统发育的分异主要受温度的影响。在全球尺度上，在系统发育拓扑树的31个节点上的279对比较中，185对气候因子的生态分化指数存在显著差异；在形态分化拓扑树的32个节点上的288对比较中，196对气候因子的生态分化指数存在显著差异。这说明，水热环境的变化是云杉属植物系统发育分化和形态分化的主要驱动因子。无论是形态分化树还是系统发育分化树，生态分化指数在较年轻的分支上大于较古老的分支，说明现代气候因子与年轻节点的分化关系更为密切。云杉属系统发育分化和形态分化的最初驱动不同，前者主要受制于热量因子，后者受制于水分因子。 关于云杉属植物性状与气候因子的关系，植物性状变异主要取决于气候因子所决定的环境梯度。具体讲，温度变异是主要的环境梯度，变化趋势为湿冷到干热，水分梯度属于次要因素。就植物性状与气候梯度的关联而言，在湿冷的环境中，具有较小针叶和种子、较大的球果和种鳞的物种往往占优势。在气候梯度上，随着性状的变异，物种之间形成了明显的替代关系。云杉植物性状的变异表征着明显的环境信号，系统发育背景对性状变异的影响微弱。性状变异完美地捕捉到了中国云杉属植物的空间替代格局；云杉物种间的性状变异展示了较窄的温度幅度和较宽泛的水分幅度，温度条件是决定物种空间分布格局的关键因素。