Craniodental traits predict feeding performance and dietary hardness in a community of Neotropical free-tailed bats (Chiroptera: Molossidae)

Form-function studies have established a strong link between dental
morphology and the mechanical properties of food items, with animals
evolving tooth shapes theoretically ideal for their diets. However,
information on how teeth perform under natural conditions is rare, which
limits our understanding of how dental morphology influences dietary
ecology and niche partitioning within animal communities. Free-tailed bats
(Chiroptera: Molossidae) are a diverse clade of aerial insectivorous
mammals that exhibit an outstanding variation in size and craniodental
traits, which have been directly related to ecological segregation among
sympatric species. We investigate the mechanisms that allow functional
dietary specialization and trophic segregation among sympatric free-tailed
bat species inhabiting a Neotropical forest. To do so, we coupled data on
3D dental topographic metrics, head and skull dimensions, field-collected
feeding performance and dietary hardness measurements. We found that
evolved differences in molar topography and skull size vary in tandem with
the mechanical demands of prey items naturally consumed by sympatric
molossid species. This may be explained by feeding performance
capabilities resulting from both molar shape and the overall size of the
feeding apparatus, which seem to allow efficient processing of prey items
with specific mechanical properties. For instance, smaller bats with
higher molar topographic values (sharper, more complex molars) and more
gracile heads mainly feed on softer insects, whereas bigger bats with
lower molar topographic values (blunter, less complex molars) and more
robust heads mostly feed on tougher insects. Species with a broader range
of sizes, craniodental morphologies, and insect hardness are also present
in the community. Our results illustrate how the morphology and size of
feeding structures, and how they perform, may facilitate trophic
segregation among sympatric insectivorous bats. Similar mechanisms may
help structure other communities of insectivorous mammals, therefore the
approaches presented here could be used to generate a better understanding
of the ecomorphological traits and processes that underlie their
diversity.

形态-功能研究已证实牙齿形态（dental morphology）与食物的机械特性（mechanical properties）之间存在紧密关联，动物演化出的齿形理论上适配其食谱需求。然而，关于牙齿在自然条件下功能表现的相关资料极为匮乏，这限制了我们对牙齿形态如何影响动物群落内的饮食生态与生态位分化的认知。游离尾蝠（翼手目Chiroptera：犬吻蝠科Molossidae）是一类多样化的空中食虫哺乳动物类群，其体型与颅齿特征（craniodental traits）存在显著差异，且该差异与同域物种（sympatric species）间的生态分隔（ecological segregation）直接相关。本研究针对栖息于新热带林的同域游离尾蝠物种间的功能食性特化与营养分隔（trophic segregation）机制展开探究。为此，我们整合了三维牙齿地形学指标（3D dental topographic metrics）、头部与头骨尺寸、野外采集的取食功能表现数据以及食物硬度测量数据。研究发现，臼齿地形（molar topography）与头骨尺寸的演化差异，与同域犬吻蝠科物种天然捕食猎物的机械需求协同变化。这一现象可通过臼齿形态与取食器官（feeding apparatus）整体尺寸共同决定的取食功能能力来解释，该能力可高效处理具备特定机械特性的猎物。例如，臼齿地形值更高（齿更尖锐、结构更复杂）且头部更纤细的小型蝙蝠，主要取食柔软昆虫；而臼齿地形值更低（齿更钝圆、结构更简单）且头部更粗壮的大型蝙蝠，则多以更坚韧的昆虫为食。该群落中还存在体型、颅齿形态与猎物硬度跨度更广的物种。本研究结果阐明了取食结构的形态与尺寸，及其功能表现，如何促进同域食虫蝙蝠间的营养分隔。类似机制或可助力构建其他食虫哺乳动物群落，因此本研究采用的方法可用于更深入地解析支撑其物种多样性的生态形态学特征（ecomorphological traits）与过程。