Instituto de Ecología, Universidad Nacional Autónoma de México, AP70-275, Mexico City 04510, Mexico.
J Exp Biol. 2012 Nov 15;215(Pt 22):3989-96. doi: 10.1242/jeb.068494. Epub 2012 Aug 16.
Mammals frequently use nectar as a supplementary food, while a predominantly nectarivorous lifestyle with morphological specializations for this feeding mode is rare within the class. However, Neotropical flower-visiting bats largely depend on nectar resources and show distinct adaptations to a nectar diet. Glossophagine bats form local guilds of 2-6 species that may differ distinctly in skull morphology. It is still unknown how and to what extent this morphological diversity influences the efficiency of nectar extraction and hence resource partitioning within the local bat guild. As foraging behaviour is a key factor for niche partitioning of co-existing species, we compared nectar extraction behaviour and efficiency at different flower depths among sympatric bat species with different degrees of morphological specialization (Glossophaga soricina, Leptonycteris yerbabuenae and Musonycteris harrisoni). In flight cage experiments with artificial flowers, at deeper nectar levels all species showed a distinct decrease in the amount of nectar extracted per visit and an increase in the time spent hovering at the flower, indicating increased energetic cost when foraging on longer tubed flowers. The lowest nectar extraction efficiency (g s(-1)) was found in the small G. soricina and the highest in the largest species L. yerbabuenae. However, when also considering the different energy requirements of the different-sized bat species, the morphologically most specialized M. harrisoni consistently showed the highest foraging efficiency. Our data suggest that the long rostrum and tongue of the extremely specialized M. harrisoni are probably not evolved for monopolization of co-evolved deep flowers but for allowing efficient access to the broadest range of the local chiropterophilous flower resources.
哺乳动物经常将花蜜作为补充食物，而在哺乳纲中，具有形态特化以适应这种摄食方式的主要以花蜜为食的生活方式则较为罕见。然而，新热带区访花蝙蝠在很大程度上依赖花蜜资源，并表现出对花蜜饮食的明显适应。 glossophagine 蝙蝠形成 2-6 种的局部行会，其头骨形态可能有明显的差异。目前还不清楚这种形态多样性如何以及在多大程度上影响花蜜提取的效率，从而影响当地蝙蝠行会内的资源分配。由于觅食行为是共存物种生态位分化的关键因素，我们比较了具有不同形态特化程度（ Glossophaga soricina 、 Leptonycteris yerbabuenae 和 Musonycteris harrisoni ）的共生蝙蝠物种在不同花朵深度的花蜜提取行为和效率。在带有人工花朵的飞行笼实验中，在较深的花蜜水平下，所有物种在每次访问中提取的花蜜量明显减少，在花朵上盘旋的时间增加，这表明在较长的管状花朵上觅食时能量消耗增加。在小 G. soricina 中发现最低的花蜜提取效率（ g s(-1) ），而在最大的物种 L. yerbabuenae 中发现最高的花蜜提取效率。然而，当也考虑到不同大小蝙蝠物种的不同能量需求时，形态上最特化的 M. harrisoni 始终表现出最高的觅食效率。我们的数据表明，极度特化的 M. harrisoni 的长吻和长舌可能不是为了垄断共同进化的深花而进化的，而是为了能够有效地利用当地的翼手目植物资源。
