西沙岛屿植物群落的传粉网络及其动态结构研究

The composition of island communities provides excellent materials for the study of the dispersal, formation and differentiation of species; Oceanic islands have long been regarded as “natural laboratories” for evolutionary ecological studies. The diversity and composition of community species may shape the network structure, which will affect the pollination and fructification of plants. Studies in the structure of the pollination function group and pollination network of oceanic island communities will provide new evidence for the evolution of the pollination system and theoretical basis for the construction of ecological environment in the South China Sea. On the other hand, few studies have been focused on how species diversity and composition affected these pollination network assemblages. In this proposal, we plan to conduct a three-year study of pollination networks at community level on Paracel Islands. Firstly, by investigating the species diversity and composition in fixed communities during flowering seasons, and observing the pollinator visitations and frequencies of the flower of generalization and specialization, we aim to construct the dynamical visitation networks between plants and pollinators. Meanwhile, by investigating the pollen qualities and quantities on pollinators and stigmas of each plant species, we aim to construct dynamical heterospecific pollen transfer networks. Finally, we will study how species diversity and composition shape the structures and dynamical features of pollination networks, heterospecific pollen transfer networks and the parasitic networks in oceanic islands, also the potential effects on seed productions of plant species at community level, thus improve pollination network studies into the plant reproduction, which may also shed more lights on the mechanisms behind the maintaining of biodiversity and ecological restoration of oceanic islands.

岛屿生物群落的组成为研究物种的散布、形成与分化提供了极好的原材料，海洋岛屿被誉为进化生态学研究的“天然实验室”。群落物种多样性和构成等因素，都可能塑造网络结构，进而影响植物的授粉和结实。探讨海洋岛屿群落传粉功能群和传粉网络的结构，将为传粉系统的演化提供新证据，并为我国南海岛礁建设中的生态环境建设提供理论依据。本项目拟在前期工作基础上，选择我国南端西沙群岛的永兴岛的典型、代表性的植物群落，定点调查开花植物的多样性和构成，通过定量分析相对泛化和特化的花的传粉者种类和访问频率、传粉者携带和柱头落置的花粉种类和数目，构建动态的访问和种间花粉流网络。探讨岛屿群落物种多样性和构成，对访问网络、花粉流网络及寄生网络结构的影响，探索岛屿生态网络的塑造机制和对群落植物结实的潜在作用，将生态网络的研究深入到植物间对繁殖的相互影响，为理解岛屿生物多样性的维持机制和生态修复提供依据。

岛屿生物群落的组成为研究物种的散布、形成与分化提供了极好的原材料，海洋岛屿被誉为进化生态学研究的“天然实验室”。植物与传粉者相互作用的传粉网络是一个动态的实体，植物开花物候的季节性变化可以在短时间和长时间内重塑其结构。然而，很少有研究考虑到这种季节性动态变化，特别是海洋岛屿群落的传粉网络。探讨海洋岛屿群落传粉功能群和传粉网络的结构，将为传粉系统的演化提供新证据，并为我国南海岛礁建设中的生态环境建设提供理论依据。本项目选择我国西沙群岛的永兴岛的典型、代表性的植物群落，利用春夏秋冬四个季节的植物与传粉者间相互作用的数据，分析了四个季节定性的传粉网络结构的动态变化，研究了永兴岛群落传粉网络的季节性动态变化。在这四个季节中，分别收集了连续两个月的植物与传粉者相互作用的数据，并计算了四个网络水平的指标来表征传粉网络的总体结构。采用群落差异性统计分析方法，对群落四个季节的网络结构参数进行比较分析，探讨影响这种动态变化格局的潜在因素。同时计算并比较了植物和传粉功能群在物种水平的网络指标的季节动态变化。研究结果表明，永兴岛群落网络水平的特化性和模块化在四个季节的变化均与植物物种丰富度的变化呈明显相反的变化趋势。开花植物种类的增加可能促进了传粉者之间更激烈的竞争，从而导致生态位重叠的增加，引起传粉网络特化性和模块化的下降，反之亦然。进一步分析表明，传粉网络的季节动态变化的内在驱动力是植物与传粉者间连接的重新组合。因此，传粉者之间生态位重叠的季节性变化导致了植物与传粉者间相互作用的重组，从而推动了该群落内植物与传粉者间相互作用的更替变化。在物种水平上，与其它传粉功能群相比，天蛾类传粉者最特化，而蜜蜂科传粉者的物种作用强度最大。本项目的研究成果揭示了岛屿群落物种多样性和构成对植物-传粉者互作网络的影响，为理解岛屿生物多样性的维持机制和生态修复提供了理论依据。