土地利用方式对自然群落传粉网络、花粉限制和野生植物生殖成功的影响

Pollination is an essential process in the sexual reproduction of seed plants and a key ecosystem service to human welfare. It plays a critical role in the maintenance of biodiversity and also crop yield production. Approximately 88% of the angiosperm species rely on animals for reproduction, and 70% of the major crop species worldwide are at least partly reliant on animal pollination for yield production, accounting for 35% of global food production. Many populations of pollinators appear quite vulnerable to global change, and there is concern that losses of their services could threaten native plant biodiversity, ecosystem stability and food security. However, the degree to which environment change will decrease plant reproductive success through alterations in the service of pollinators is not clear and assessing this is an important and pressing area of research, especially at the community level. Pollination study across landscape gradients can be used to investigate the effects of non-random species loss in response to global change, whereas most previous research has been based on randomly assembled communities. For example, regions with natural and human-generated landscape gradients are emerging as an ideal system to assess whether and how land use affect pollinator-plant interactions and thus plant reproduction. .The present project tries to assess pollination network, pollen limitation and thus plant reproductive success across a natural-agriculture landscape gradient from Qizimei Mountains Nature Reserve, Hubei to the neighbor town (Reserve core area, Reserve buffer area, Reserve experimental area, agriculture landscape). In each landscape level, we choose 5 natural plant communities as the research sites according to their distances to the agriculture area (less than 100m, 100-500m, 500m-1km，1km-2km，more than 2km). We would like to reveal the spatiotemporal variation in pollen network, pollen limitation and plant reproductive success along landscape gradients and among years, and clarify the effects of land use change on pollination and plant reproduction. Specially, we will answer the following four questions. Firstly, what species of pollinators are present in landscapes that are far from agriculture, but cannot persist near agricultural landscapes? Perhaps the traits of these pollinators can explain why some plant species are more sensitive to pollinators than others. Secondly, for a single species, whether pollen limitation became stronger as the population located closer to the agricultural region? If yes or no, which mechanisms are behind it? Thirdly, for multiple species, whether the effects of land use on pollen limitation were correlated with plant traits, pollinator types, and also plant diversity in the community? Finally, at the community level, whether and how land use changes affect pollinator-plant interactions? Whether the land use effects are related to habitat type, crop type and distance to agriculture area?

传粉是种子植物有性生殖不可或缺的一个环节，更是生态系统的一个关键服务功能，对维持植物群落和生态系统稳定、保障栽培作物的产量都至关重要。然而，全球变化尤其是土地利用方式的改变使动物传粉者日益减少，这可能会带来毁灭性的后果。沿着特定环境梯度进行传粉研究可以揭示全球变化导致的非随机物种丧失的作用机制，由自然系统和人工系统交织而成的环境就为开展比较研究提供了现成的梯度格局。本项目拟沿湖北省七姊妹山国家自然保护区到相邻城镇区的四个生境梯度（核心区、缓冲区、实验区、城镇区），各生境梯度内选择距其中农业区不同距离梯度的五个自然群落作为研究样地，采用分段回归模型定量评估花粉质量和数量限制。本研究将揭示传粉网络、花粉限制和植物生殖成功沿着环境梯度的时空动态变化，并在物种水平和群落水平阐明土地利用方式变化对自然群落传粉系统的影响机制，这些结果将直接服务于全球变化时代大背景下生物多样性保护需求。

传粉是生态系统的一个关键服务功能，对维持植物群落和生态系统稳定、保障栽培作物的产量都至关重要。然而，全球变化下动物传粉者日益减少引发了人们的高度关注，沿着特定环境梯度进行传粉研究可以揭示全球变化导致的非随机物种丧失的作用机制。本项目在从保护区到农耕区的不同环境梯度和生境类型共构建了57个观察样方，进行为期3年的调查，系统研究了夏季开花植物群落中植物和访花昆虫的多样性以及传粉网络的时空动态变化。结果表明环境梯度不影响开花植物的α多样性，但生境类型显著影响开花植物的α多样性和β多样性组成。与之相反，生境类型不影响但是环境梯度显著影响传粉者功能群的α多样性，并且环境梯度和年份之间具有显著的交互作用。非常重要的是，我们发现保护区内自然生境中的开花植物组成在逐年趋同，传粉者功能群在数量上组成上也随之发生了明显的变化。传粉网络结构特点主要受物种丰富度的影响，并不受生境类型和环境梯度的影响。网络水平和物种水平上，传粉网络和传粉者的特化度都呈现逐年下降的趋势，这与物种组成在年际间的变化相关。在群落、功能群和物种水平研究了盗蜜的影响，结果表明无论在群落还是功能群水平，去除盗蜜都不显著影响传粉网络的结构特征。但去除盗蜜者之后，传粉网络的特化度的变异程度降低，嵌套度的变异程度增加。在物种水平，盗蜜对齿萼凤仙花的影响是中性的，其结实率的差异并不能由传粉差异来解释。本项目的研究证明植物-传粉者之间的关系并非恒定，干扰之下导致的植物物种组成的变化会引起传粉者丰度、组成和访问行为的改变，要像大样地研究一样对植物-传粉者相互作用网络进行长期监测才可以正确评估人类干扰的影响。此外，利用SSR标记分析了华蟹甲的遗传多样性和遗传结构，结果表明其遗传多样性和遗产结构与其扩散模式相一致，这说明小地理尺度上通过遗传回溯、检测和监控物种的扩散是行之有效的研究手段，这在物种保护、监控和管理的实际应用中具有非常重要的意义。

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