没有能量就没有进化，光合作用推动了近海生物的适应性进化。本文从三个方面考察了这个进化过程的分子机制：（1）对垂直方向上光照变化的响应：原绿球藻是是地球上数量最为巨大的光合生物。它的两种生态型分别适应高光强和低光强条件。叶绿素a和b的比率是区分这两种生态型的标志性特征。我们的分析结果揭示了原绿球藻的祖先是典型的低光强适应类型。在它们叶绿素b/a比率调节发生定向进化后产生了辐射适应。叶绿素a加氧酶基因中的重组作用和Clp蛋白酶中的正选择作用（P﹤0.05）推动了原绿球藻的定向进化；（2）对水平方向上光照变化的响应：近海海域环境的一个特征是它的复杂性，特别是中国近海海域。我们发现在响应复杂的人类活动影响中，本地种类群贡献了大部分的群落物种丰富度和多样性（70.453%），而优势种在群落成员组成（Kendall’s τ = 0.856, P = 2.67 × 10-9）和结构（Kendall’s τ = 0.867, P = 2.70 × 10-9）有着决定性的作用。而光合的浮游植物和人类活动影响无显著关系，而和纬度光照有显著相关性（P﹤0.001）；（3）对其他近海生物进化的推动作用：有孔虫是一类单细胞原生动物，其中有很多类群拥有内共生的藻类为其提供能量与物质。本研究揭示了一个形成网状结构的有孔虫进化模式，包括两个重组分重组片段和一些水平基因转移事件。肌动蛋白插曲式的多样化自然选择促进了有孔虫的形态多样性（P﹤0.01）。在有孔虫主要目的分化和环圈虫科适应藻类内共生的逐步过程中发现了正选择的证据（P﹤0.01）。本研究描绘了一幅近海光合生物在垂直和水平方向上的全方位适应性演化和分布、并且助推其他生物的进化的概略图景。
其他摘要
No energy, no evolution. Photosynthesis drives adaptive evolution of organisms in coastal seas. This study investigates into molecular mechanisms involved in this adaptive evolution from three aspects. (1) Response to vertical illumination variations: Prochlorococcus is the most abundant photosynthetic organism on Earth. Two ecotypes are adapted to either high-light or low-light conditions. The ratio between chlorophyll a and b is a distinguishing characteristic of the two ecotypes. Our analyses reveal that the ancestor of Prochlorococcus was typically low-light-adapted. There was an adaptive radiation after directional evolution in the chlorophyll b/a ratio regulation. Recombination in chlorophyllide a oxygenase (CAO) and positive selection on Clp protease (P﹤0.05) contributed to the directional evolution of Prochlorococcus. (2) Response to horizontal illumination variations: Anthropogenic plus oceanographic factors in coastal waters are generally featured by their intricate complexity and unpredictable variability, especially in Chinese coastal seas. Endemic groups contribute a great majority to community richness and diversity (70.453%), and dominant species play a decisive role in community membership (Kendall’s τ = 0.856, P = 2.67 × 10-9) and structure (Kendall’s τ = 0.867, P = 2.70 × 10-9). However the phytoplankton communities showed no correlation with human impacts but the illumination on different latitudes. (3) Promotion of adaptive evolution of other organisms in coastal seas: Foraminifera is a group of single-celled protists, many groups of it host symbiotic algae for energy and materials. A reticulate evolution including two recombinant segments and several horizontal gene transfer events was revealed. Episodic diversifying selections on actin (P﹤0.01) with variant structural and functional implications further promote the morphological diversity of Foraminifera. Evidences for Darwinian positive selection were testified on the divergence of main orders and the progressive adaptation of soritids to algal symbiosis (P﹤0.01). This study outlines a picture that the omnibearing adaptive evolution of photosynthetic organisms promotes evolution of other organisms in coastal seas.
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