青藏高原及周边高山地区的植物繁殖生态学研究进展

青藏高原及周边高山地区孕育了极为丰富的植物多样性资源, 研究该地区植物如何顺利完成繁殖过程有助于我们理解植物对典型高山环境的进化和适应机制。该文综述了青藏高原地区高山植物在资源分配、繁殖方式、花部特征演化等方面的研究进展, 包括全球气候变化对植物繁殖特征的影响, 以及一些新技术和新方法在本研究领域的应用。在高山地区限制性环境中, 随海拔升高, 繁殖分配通常表现出增大的趋势, 其中投入到雄性资源的比例上升, 但具体的资源分配模式还要取决于植株的交配系统、个体大小、生活史特征、遗传特性以及环境中的资源有效性等。面对资源和传粉的双重限制, 植物在不同繁殖方式之间存在权衡, 当传粉者稀少时, 克隆繁殖和自交有利于繁殖保障; 而有性繁殖和异交能够提高种子的质量和后代的遗传多样性, 从而在复杂多变的气候条件下有利于种群的维持。因此, 不同繁殖方式的结合以及泛化的传粉互作网络可能是应对高山限制性环境的最优选择。花部特征的演化主要受到当地传粉者的选择压力, 但是外来传粉者、植食者、盗蜜者以及非生物环境(如温度、雨水和紫外辐射等)对花部性状的影响越来越受到重视。近年来, 青藏高原因其脆弱性和对气候变化的高度敏感性而在全球气候变化研究中备受关注, 以全球变暖和氮沉降增加为显著特征的全球气候变化正在直接或间接地影响着该地区高山植物的繁殖特征。气候变化影响植物和传粉者的物候并引起物种的迁移, 最终将导致植物与传粉者的时空不匹配。植物通过改变花部特征(花展示、花冠结构、花报酬的数量和质量)来响应气候变化, 这可能会改变其传粉者的类型、数量和访花行为, 从而最终影响植物的繁殖成功。3D打印和高通量测序等新技术和新方法的应用有助于促进植物繁殖生态学研究的进一步发展。3D打印的花能够精确控制其形态构造, 可以用于研究精细的花部特征变化对于传粉者行为的影响, 在此基础上与人工饲养的传粉者结合使用, 有助于进一步研究传粉者介导的花部特征演化。随着高通量测序技术的发展, 植物繁殖生态学领域, 尤其是花部特征演化的许多重要问题的潜在机制得以深入研究。该文最后提出了目前研究中需要注意的问题以及值得深入研究的发展方向。

Processes on reproductive ecology of plant species in the Qinghai-Xizang Plateau and adjacent highlands

The Qinghai-Xizang Plateau and its adjacent highlands host a rich plant diversity, and understanding on how plant species reproduce successfully in those high mountain regions would be of great help for us to discover the evolution and adaptability of plants to the typical alpine environments. Here, we reviewed the progresses of plant reproductive ecology in the Qinghai-Xizang Plateau and its adjacent highlands, with emphases on resource allocation, reproductive mode, evolution of floral traits, etc. We also summarized the impacts of global climate changes on plant reproduction, and the applications of new technologies and methods in this research field to explore the potential mechanisms of plant evolution and adaptation. In the stressful environments of high mountain areas, with the increase of altitude, the reproductive allocation usually shows a trend of increase, and the proportion of resources invested in male function also increases. However, the specific pattern of resource allocation strongly depends on the mating system, individual size, life history, genetic variation and resource availability. In the context of resource and pollination limitation, plants will weight different reproductive modes. Clonal reproduction and self-pollination are conductive to reproductive assurance in populations with pollinator scarcity, while sexual reproduction and cross-pollination can improve seed quality and genetic diversity of offspring, which could benefit population survival in the potential climate flunctations. Therefore, the combinations of different reproductive modes and the generalized pollination networks may be the good choices to adapt to the stressful environments of highlands. The evolution of floral traits might be mainly driven by the selective pressure of local pollinators, but more and more attentions have been paid to the effects of exotic pollinators, herbivores, nectar robbers and abiotic environments such as temperature, precipitation and ultraviolet radiation on floral traits. In recent years, the Qinghai-Xizang Plateau has become one of research hotspots because of its fragility and sensitivity to climate change. Global climate change, characterized by global warming and increased nitrogen deposition, is directly or indirectly affecting the reproductive characteristics of plant species in the region. Climate change may cause shifts of phenology and distribution area of plants and pollinators, which leads to temporal decoupling and spatial mismatch between them. Plants can respond to climate change by adjusting floral traits (floral display, corolla structure, quantity and quality of reward), which may result in changes of type, amount and foraging behaviors of pollinators and affect reproductive success of plants at last. The applications of new technologies and methods could advance our knowledge on plant reproductive ecology. 3D printed flowers could control floral traits precisely and could be employed in examining the effects of subtle changes of floral traits on pollinator behaviors, which would be useful in understanding pollinator mediated selection on floral traits in combination with the uses of commercial pollinators. Importantly, with the development of high-throughput sequencing, the underlying mechanisms of important topics in plant reproductive ecology could be discovered more easily than before, especially in the field of floral evolution. As a conclusion, key issues that need additional attention in the current research as well as the fields worthy of further study are highlighted.