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.

物种特化在生物相互作用网络中对网络稳定性与生态系统功能具有关键调控作用。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）如何影响互利共生网络内的物种特化提供重要视角。本研究基于蜂鸟丰度与资源（花蜜）的独立测定数据、蜂鸟性状信息以及蜂鸟-植物相互作用数据，在厄瓜多尔南部安第斯山区的三类生境（森林、灌丛、牧场）中，于两年内开展10次采样，以此探究资源可获得性与物种形态如何影响蜂鸟的特化水平。本研究采用三类指数衡量网络中蜂鸟物种的特化程度：d’（与生态位分化相关）、泛化度（generality，与生态位宽度相关）以及PSI（与传粉服务相关）。分析结果显示，蜂鸟物种的三类特化指数均受资源可获得性的显著影响：所有指数均表明，当资源可获得性降低时，蜂鸟的特化程度显著升高。此外，d’的变异还可由资源可获得性与喙长的交互作用解释：长喙蜂鸟在资源可获得性较低时特化程度高于其他物种，而在资源可获得性较高时则与其他物种特化程度相当。总体而言，本研究结果凸显了生态与进化因子对生物相互作用网络中物种特化的调控重要性。本研究特别证实，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。传粉者沿资源梯度的特化变化，会对动物传粉等生态系统功能产生重要影响。