Data from: Effects of hummingbird morphology on specialization in pollination networks vary with resource availability

Specialization of species in interaction networks influences network stability and ecosystem functioning. Spatial and temporal variation in resource availability may provide insight into how ecological factors, such as resource abundance, and evolutionary factors, such as phylogenetically conserved morphological traits, influence specialization within mutualistic networks. We used independent measures of hummingbird abundance and resources (nectar), information on hummingbird traits and plant–hummingbird interactions to examine how resource availability and species' morphology influence the specialization of hummingbirds in three habitat types (forest, shrubs, cattle ranch) sampled over 10 sessions across two years in the southern Andes of Ecuador. Specialization of hummingbird species in the networks was measured by three indices: d' (related to niche partitioning), generality (related to niche width) and PSI (related to pollination services). Specialization indices d', generality and PSI of hummingbird species were influenced by resource availability. All indices indicated that specialization of hummingbirds increased when the availability of resources decreased. Variation in d' was also explained by an interaction between resource availability and bill length; hummingbirds with a long bill switched from being more specialized than other species when resource availability was low to being similarly specialized when availability was high. Overall, our results highlight the importance of ecological and evolutionary factors determining the specialization of species in interaction networks. We demonstrate in particular that ecological gradients in resource availability cause substantial changes in consumers' foraging behavior contingent on their morphology. Changes in pollinator specialization along resource gradients can have impacts on ecosystem functions, such as pollination by animals.物种互作网络中的物种种化程度，会影响网络稳定性与生态系统功能。资源可获得性的时空变异，可为解析生态因子（如资源丰度）与进化因子（如系统发育保守的形态性状）如何调控互利共生网络内的物种特化提供重要线索。本研究依托蜂鸟多度与资源（花蜜）的独立测定数据、蜂鸟性状信息以及植物-蜂鸟互作数据，针对厄瓜多尔南部安第斯山区的森林、灌丛、牧场三类生境，探究了资源可获得性与物种形态如何影响蜂鸟的特化程度；研究在两年内共开展10次采样。我们通过三类指标量化网络中蜂鸟物种的特化程度：d'（关联生态位分化）、泛化度（generality，关联生态位宽度）以及PSI（关联传粉服务）。蜂鸟物种的三类特化指数d'、泛化度与PSI均受资源可获得性的调控。所有指数均显示，当资源可获得性降低时，蜂鸟的特化程度显著升高。d'的变异还可通过资源可获得性与喙长的交互效应加以解释：当资源可获得性较低时，长喙蜂鸟的特化程度高于其他物种；而当资源可获得性较高时，长喙蜂鸟与其他物种的特化程度并无显著差异。总体而言，本研究结果凸显了生态与进化因子对物种互作网络中物种种化程度的关键调控作用。我们特别证实，资源可获得性的生态梯度会依据消费者的形态特征，显著改变其觅食行为。沿资源梯度发生的传粉者特化变化，会对动物传粉等生态系统功能产生重要影响。