Phenological patterns and pollination network structure in a Venezuelan páramo: a community-scale perspective on plant-animal interactions

Background: Little information is available about life history of páramo plants such as phenology and plant-animal interactions.
Aims: We analysed phenological patterns of flowering and characterised the structure of a plant-pollinator network in a Venezuelan páramo in order to identify key species in this ecosystem.
Methods: We counted the number of individuals with flowers of 76 native plant species and recorded their pollinators in 16 permanent plots between 3000 and 4200 m monthly for three years. We used this dataset to develop a plant-pollinator network, on which nine different metrics related to structural properties were calculated.
Results: The flowering of most species concentrated during the rainy season (between May and November), however some species have continuous flowering. The guild of floral visitors included hummingbirds, flower piercers, bumblebees, Diptera and Lepidoptera. The plant – flower visitor interaction network did not exhibit nestedness, but showed a significant specialization index (H2) and high values of functional complementarity.
Conclusions: Páramo plants have the capacity of maintaining a resident nectarivorus fauna (bumblebees and hummingbirds) because of continuous flower offer during the year. However, the plant – pollinator network identified could be very sensitive to the loss component species, owing to high levels of specialisation and functional complementarity.

研究背景：目前关于帕拉莫（páramo）植物的生活史，如物候学以及植物与动物的相互作用等相关信息仍较为匮乏。
研究目标：本研究针对委内瑞拉境内一处帕拉莫生态系统，分析其开花物候模式，并对植物-传粉者网络的结构进行表征，以期识别该生态系统中的关键物种。
研究方法：本研究在海拔3000至4200米的16个永久样地中，连续三年每月对76种本土开花植物的开花个体数进行统计，并记录其传粉者。基于该数据集构建植物-传粉者网络，并计算9项与网络结构特性相关的指标。
研究结果：多数物种的花期集中于雨季（5月至11月），但部分物种可全年持续开花。花访客类群包括蜂鸟、啄花昆虫、熊蜂、双翅目昆虫以及鳞翅目昆虫。该植物-花访客相互作用网络未表现出嵌套性，但呈现出显著的特化指数（H2）以及较高的功能互补性水平。
研究结论：帕拉莫植物可通过全年持续提供开花资源，维持定居性食蜜动物群（熊蜂与蜂鸟）的存续。然而，由于该网络具有较高的特化程度与功能互补性，本研究识别出的植物-传粉者网络对部分物种的丧失可能具有较高的敏感性。