基于系统发育探讨山茶属花色进化与传粉模式关系的研究

Floral color diversity has been often thought to be driven by pollinator mediated selection. Does floral color, therefore, reflect the visual capacities of the pollinator fauna? Or pollinator’s preference determines the evolutionary direction of floral color? Evidence to address these questions is surprisingly limited, although new insights from vision science combined with advances in phylogenetic comparative methods offer the potential for rapid advances in our understanding of the color divergence/convergence in angiosperm. Genus Camellia (Theaceae) provides a great opportunity to study the evolution of pollination-system transitions and floral color diversification. It includes around 200 species with similar floral morphology (less-specialized, open, radiate corollas) but different floral color. In the previous studies, we found sunbird-honeybee pollinated species Camellia petelotii with yellow flower in South China had sister species C. oleifera with white flower that was insect-pollinated and sister species C. polyodonta with red flower that was bird-pollinated. It maybe suggested that divergence of floral color related to pollination-system transitions. To understand the adaptive strategy of floral color in this genus, we plan to conduct comparative studies of pollination system among 25 Camellia species in Southwest China. Floral color will be quantified by measuring the reflectance spectrum of perianth and transform to pollinator's visual system. Well-resolved species-level phylogenies are necessary to interpret of ancestral states and understand the relationship between evolutionary pollination-system transitions and the evolution of floral color. Furthermore, our researches including artificial control experiment of changing the reflectance spectrum of perianth to examine the preference of pollinator. This project could not only help us understand the evolution of Camellia flower color, but also provide new insights into the role of plant-pollinator interaction in the diversification of Camellia at the species level.

植物-传粉者相互作用历来被认为是驱动花色进化的重要原因，然而，验证传粉者作用的研究大多数集中于单个物种，且较少考虑动物与人在感知方面的显著差异，因此无法探究花色在一个类群中的进化路径。山茶属是我国西南地区花形态相近，但花色分化明显的一个大属，其花色进化的适应意义有待研究。申请者在对金花茶和油茶等物种的传粉系统的研究基础上，选择我国西南地区的山茶属植物作为研究对象，计划通过对属内25个种开展花被反射光谱测定和传粉者调查，将人眼中的“花色”转换成传粉动物视觉中的“花色”，并重建山茶属的系统发育树，在系统学水平研究花色进化与传粉模式的关系。另外，选择部分花色不同的山茶进行控制实验，通过人为改变花被反射光谱来验证花色进化与传粉者偏好的相关假说。该项目的开展不仅能为探讨山茶属花色的进化路径提供直接证据，而且能为在物种水平上阐明植物-传粉者相互作用在山茶属的花部特征分化过程中的作用提供理论依据。

本项目以山茶属植物为研究材料，研究了该属植物花色与对传粉者适应的关系以及花色和传粉系统在此属内的进化转变。具体地说，为了验证不同花色的山茶属物种的传粉系统，我们对中国西南地区的14种花色不尽相同的山茶属物种开展了传粉者观察实验。对于拥有多种传粉者的山茶属物种，我们开展了传粉者筛选实验，以确定不同类型传粉者的传粉效率。为了比较人眼和传粉者视觉系统中花色的差异，我们对14种山茶属物种的花被的反射光谱进行了量化，并与传粉者的视觉系统进行了匹配。为了检测花被颜色的形成是否受胞内环境因素的影响，我们定量了花被中总黄酮的含量。为了研究山茶属植物的花色进化路径，我们重建了山茶属的系统发育关系。结果表明：(1)传粉者对不同花色的物种会表现出一定的选择偏好，但花色相近的物种并不完全能吸引相似的传粉者。(2)山茶属植物花被总黄酮含量与花被颜色之间没有呈现相关性。（3）在系统发育的框架下，山茶属植物花色的进化与传粉者功能群也没有呈现明显的相关性。综上所述，本项目探索了传粉者在山茶属花色进化中的作用，然而，植物花色的进化是一个复杂的过程，它在多大程度上受到传粉者选择还有待进一步研究。本项目的开展不仅为理解被子植物花色多样化的机理提供了参考，还为山茶属这样一类正在受到严重破坏的重要野生花卉资源的保护工作提供了背景知识。

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