Morphological diversity in the sensory system of phyllostomid bats: implications for acoustic and dietary ecology

1. Sensory systems perform fitness-relevant functions, and specialized
sensory structures allow organisms to accomplish challenging tasks.
However, broad comparative analyses of sensory morphologies and their
performance are lacking for diverse mammalian radiations. 2. Neotropical
leaf-nosed bats (Phyllostomidae) are one of the most ecologically diverse
mammal groups; including a wide range of diets and foraging behaviors, and
extreme morphological variation in external sensory structures used in
echolocation (nose leaf and pinnae). 3. We coupled 3D geometric
morphometrics and acoustic field recordings under a phylogenetic framework
to investigate the mechanisms underlying the diversification of external
sensory morphologies in phyllostomids, and explored the potential
implications of sensory morphological diversity to functional outputs and
dietary ecology. 4. We found that the nose leaf consists of two
evolutionary modules, spear and horseshoe, suggesting that modularity
enabled morphological and functional diversification of this structure. 5.
We found a significant association between some aspects of nose leaf shape
and maximum frequency and bandwidth of echolocation calls, but not between
pinnae shape and echolocation call parameters. This may be explained by
the use of multiple sensory modes across phyllostomids and plasticity of
some echolocation call parameters. 6. Species with different diets
significantly differed in nose leaf shape, specifically in spear breadth,
presence of a midrib, and cupping and anterior rotation of the horseshoe.
This may relate to different levels of prey type specificity within each
diet. Pinnae shape significantly differed between species that consume
non-mobile, non-evasive prey (broad rounded, cupped pinnae) and mobile,
evasive prey (flattened pinnae with a sharp tapering apex). This may
reflect the use of different sound cues to detect prey. 7. Our results
give insight into the morphological evolution of external sensory
structures in bats, and highlight new links between morphological
diversity and ecology.

1. 感官系统承担与适应度相关的功能，特化的感官结构赋予生物体完成高难度任务的能力。然而，针对多样化哺乳动物辐射演化类群的感官形态及其功能的大规模比较分析仍较为匮乏。
2. 新热带叶口蝠科（Phyllostomidae）是生态多样性最高的哺乳动物类群之一，其类群涵盖了多样的食性与觅食行为，且用于回声定位（echolocation）的外部感官结构——鼻叶（nose leaf）与耳廓（pinnae）——存在极端的形态变异。
3. 本研究结合系统发育框架（phylogenetic framework）下的三维几何形态测量学（3D geometric morphometrics）与野外声学录音技术，探究叶口蝠科外部感官形态演化分化的潜在机制，并探讨感官形态多样性对功能输出与食性生态的潜在关联。
4. 研究发现鼻叶由两个演化模块（evolutionary modules）构成，即矛状结构与马蹄状结构，这表明模块化特性推动了该结构的形态与功能分化。
5. 研究表明，鼻叶形态的部分特征与回声定位叫声的最大频率及带宽（bandwidth）存在显著关联，但耳廓形态与回声定位叫声参数（echolocation call parameters）之间并无此类关联。这一现象可通过叶口蝠科类群所采用的多感官模式，以及部分回声定位叫声参数的可塑性加以解释。
6. 不同食性的物种在鼻叶形态上存在显著差异，具体体现为矛状结构宽度、中脊的有无，以及马蹄状结构的凹陷与前旋。这或与各类食性下不同的猎物类型特异性相关。在捕食非移动、无逃避行为的猎物（对应宽圆凹陷状耳廓）与捕食移动、有逃避行为的猎物（对应顶端尖锐收窄的扁平状耳廓）的物种之间，耳廓形态同样存在显著差异，这或许反映了不同物种依赖不同的声音线索来探测猎物。
7. 本研究结果为蝙蝠外部感官结构的形态演化提供了新的深入见解，并揭示了形态多样性与生态之间的全新关联。