Data from: Foraging strategies of generalist and specialist Old World nectar bats in response to temporally variable floral resources

Foraging theory predicts that generalist foragers should switch resources more readily, while specialist foragers should remain constant to preferred food resources. Plant-pollinator interactions provide a convenient system to test such predictions because floral resources are often temporally patchy, thus requiring long-lived pollinators to switch resources seasonally. Furthermore, flowering phenologies range from ‘steady-state’ (low-rewarding but highly reliable) to ‘big-bang’ (high-rewarding but ephemeral) plant species. We assessed how nectarivorous Old World bats respond to this temporally variable floral environment by examining their diets throughout the year. Over 15 months of fieldwork in southern Thailand, we simultaneously: (1) recorded the flowering phenologies of six bat-pollinated plant taxa; and (2) assessed the diets of seven common flower-visiting bat species. As predicted, the generalist nectarivore (Eonycteris spelaea) frequently switched diets and utilized both big-bang and steady-state resources, while the specialist nectarivores (Macroglossus minimus and M. sobrinus) foraged on one or two steady-state plant species year-round. Our results suggest that larger and faster bat species are able to fly longer distances in search of big-bang resources, while smaller bat species rely on highly predictable food resources. This study supports the theory that generalist foragers have flexible diets, while specialist species restrict foraging to preferred floral resources even when other floral resources are more abundant. Moreover, these findings demonstrate how plant flowering phenology and pollinator diet breadth can shape the frequency and constancy of pollinator visits; we further discuss how such interactions can influence the potential extent of gene flow within a patchy floral environment.

觅食理论（Foraging theory）预测，广食性觅食者应更易转换资源，而特化觅食者则应坚守偏好的食物资源。植物-传粉者互作是检验此类预测的便捷系统，因为花资源通常在时间维度上呈斑块状分布，故而长寿命的传粉者需要在不同季节转换资源。此外，植物的开花物候（flowering phenologies）涵盖从「稳态型」（低奖励但高度可靠）到「大爆发型」（高奖励但花期短暂）的各类群。
我们通过全年监测食蜜蝙蝠的食谱，评估了旧大陆（Old World）食蜜蝙蝠对这种时间异质性花境的响应。在泰国南部开展的为期15个月的野外调查中，我们同时完成了两项工作：(1) 记录6种蝙蝠传粉植物类群的开花物候；(2) 评估7种常见访花蝙蝠的食谱。
正如预测，广食性食蜜者——大长舌果蝠（Eonycteris spelaea）——会频繁转换食谱，同时利用「大爆发型」和「稳态型」资源；而特化食蜜者——小长舌果蝠（Macroglossus minimus）与（M. sobrinus）——全年仅取食1至2种稳态型植物。我们的研究结果显示，体型更大、飞行速度更快的蝙蝠物种能够飞行更远距离以搜寻「大爆发型」资源，而体型较小的蝙蝠则依赖高度可预测的食物资源。
本研究佐证了「广食性觅食者食谱具有灵活性，而特化物种即便在其他花资源更为丰富的情况下，仍会将觅食范围限定在偏好的花资源上」这一理论。此外，这些发现揭示了植物开花物候与传粉者食谱宽度如何塑造传粉者访花的频率与持续性；我们还进一步讨论了此类物种互作如何影响斑块状花境中种群内基因流动（gene flow）的潜在范围。