Bender Irene M A, Kissling W Daniel, Böhning-Gaese Katrin, Hensen Isabell, Kühn Ingolf, Wiegand Thorsten, Dehling D Matthias, Schleuning Matthias
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.
Institute of Biology, Geobotany and Botanical Garden, Martin-Luther-University Halle-Wittenberg, Am Kirchtor 1, 06108, Halle, Germany.
J Anim Ecol. 2017 Jul;86(4):800-811. doi: 10.1111/1365-2656.12683. Epub 2017 May 10.
Interactions between resource and consumer species result in complex ecological networks. The overall structure of these networks is often stable in space and time, but little is known about the temporal stability of the functional roles of consumer species in these networks. We used a trait-based approach to investigate whether consumers (frugivorous birds) show similar degrees of functional specialisation on resources (plants) in ecological networks across seasons. We additionally tested whether closely related bird species have similar degrees of functional specialisation and whether birds that are functionally specialised on specific resource types within a season are flexible in switching to other resource types in other seasons. We analysed four seasonal replicates of two species-rich plant-frugivore networks from the tropical Andes. To quantify fruit preferences of frugivorous birds, we projected their interactions with plants into a multidimensional plant trait space. To measure functional specialisation of birds, we calculated a species' functional niche breadth (the extent of seasonal plant trait space utilised by a particular bird) and functional originality (the extent to which a bird species' fruit preference functionally differs from those of other species in a seasonal network). We additionally calculated functional flexibility, i.e. the ability of bird species to change their fruit preference across seasons in response to variation in plant resources. Functional specialisation of bird species varied more among species than across seasons, and phylogenetically similar bird species showed similar degrees of functional niche breadth (phylogenetic signal λ = 0·81) and functional originality (λ = 0·89). Additionally, we found that birds with high functional flexibility across seasons had narrow functional niche breadth and high functional originality per season, suggesting that birds that are seasonally specialised on particular resources are most flexible in switching to other fruit resources across seasons. The high flexibility of functionally specialised bird species to switch seasonally to other resources challenges the view that consumer species rely on functionally similar resources throughout the year. This flexibility of consumer species may be an important, but widely neglected mechanism that could potentially stabilise consumer-resource networks in response to human disturbance and environmental change.
资源物种与消费物种之间的相互作用形成了复杂的生态网络。这些网络的整体结构在时空上通常是稳定的，但对于消费物种在这些网络中的功能角色的时间稳定性却知之甚少。我们采用基于性状的方法来研究消费者（食果鸟类）在不同季节的生态网络中对资源（植物）的功能专业化程度是否相似。我们还测试了亲缘关系相近的鸟类物种是否具有相似程度的功能专业化，以及在某个季节中对特定资源类型具有功能专业化的鸟类在其他季节切换到其他资源类型时是否具有灵活性。我们分析了来自热带安第斯山脉的两个物种丰富的植物 - 食果动物网络的四个季节重复样本。为了量化食果鸟类对果实的偏好，我们将它们与植物的相互作用投射到多维植物性状空间中。为了衡量鸟类的功能专业化程度，我们计算了一个物种的功能生态位宽度（特定鸟类利用的季节性植物性状空间的范围）和功能独特性（一个鸟类物种的果实偏好与季节性网络中其他物种的功能差异程度）。我们还计算了功能灵活性，即鸟类物种响应植物资源变化而在不同季节改变其果实偏好的能力。鸟类物种的功能专业化在物种间的差异大于在不同季节间的差异，并且系统发育相似的鸟类物种表现出相似程度的功能生态位宽度（系统发育信号λ = 0·81）和功能独特性（λ = 0·89）。此外，我们发现跨季节具有高功能灵活性的鸟类每个季节的功能生态位宽度较窄且功能独特性较高，这表明在季节上专门针对特定资源的鸟类在跨季节切换到其他果实资源时最为灵活。功能专业化的鸟类物种在季节上切换到其他资源的高灵活性挑战了消费物种全年依赖功能相似资源的观点。消费物种的这种灵活性可能是一种重要但广泛被忽视的机制，它有可能在应对人类干扰和环境变化时稳定消费 - 资源网络。
