Data from: Specialization and phenological synchrony of plant–pollinator interactions along an altitudinal gradient

1. One of the most noticeable effects of anthropogenic climate change is the shift in timing of seasonal events towards earlier occurrence. The high degree of variation in species' phenological shifts has raised concerns about the temporal decoupling of interspecific interactions, but the extent and implications of this effect are largely unknown. In the case of plant–pollinator systems, more specialized species are predicted to be particularly threatened by phenological decoupling, since they are assumed to be less flexible in the choice of interaction partners, but until now this hypothesis has not been tested. 2. In this paper, we studied phenology and interactions of plant and pollinator communities along an altitudinal gradient in the Alps as a model for the possible effects of climate change in time. 3. Our results show that even relatively specialized pollinators were much more flexible in their use of plant species as floral resources than their local flower visitation suggested. We found no relationship between local specialization of pollinators and the consistency of their visitation patterns across sites, and also no relationship between specialization and phenological synchrony of pollinators with particular plants. 4. Thus, in contrast to the conclusions of a recent simulation study, our results suggest that most pollinator species included in this study are not threatened by phenological decoupling from specific flowering plants. However, the flexibility of many rarely observed pollinator species remains unknown. Moreover, our results suggest that specialized flower visitors select plant species based on certain floral traits such as the length of the nectar holder tube. If that is the case, the observed flexibility of plant–pollinator interactions likely depends on a high degree of functional redundancy in the plant community, which may not exist in less diverse systems.

1. 人为气候变化最显著的影响之一，便是各类季节性事件的发生时序逐步向更早节点偏移。不同物种的物候偏移（phenological shift）幅度存在极高异质性，这引发了学界对种间相互作用时间解耦（temporal decoupling）的担忧，但该效应的波及范围与潜在影响在很大程度上仍未明确。以植物-传粉者（plant-pollinator）系统为例，高度特化的物种被认为更易受到物候解耦的威胁，因其在交互伙伴的选择上灵活性相对不足，但截至目前这一假说尚未得到实证验证。
2. 本研究以阿尔卑斯山脉沿线的海拔梯度（altitudinal gradient）作为气候变化时序效应的研究模型，对当地植物与传粉者群落的物候特征及相互作用关系展开了系统性调查。
3. 研究结果表明，即便是相对特化的传粉者，其在选取植物作为花类资源时的灵活性，也远高于其当地访花行为所体现的水平。我们未发现传粉者的局部特化程度与其跨样地访花模式的稳定性存在关联，亦未发现特化程度与传粉者与特定植物的物候同步性之间存在相关性。
4. 综上，与近期一项模拟研究的结论相悖，本研究结果显示，本次纳入研究的多数传粉者物种，并不会受到与特定显花植物发生物候解耦的威胁。不过，许多罕见观测到的传粉者物种的交互灵活性仍未明确。此外，本研究结果显示，特化访花者会基于特定花部性状（如蜜管长度）来选择植物物种。若该结论成立，则观测到的植物-传粉者相互作用的灵活性，大概率依赖于植物群落中高度的功能冗余（functional redundancy），而这一特征在多样性更低的群落中可能并不存在。