Data from: Primary productivity explains size variation across the Pallid bat’s (Antrozous pallidus) western geographic range

1. Body size is associated with many aspects of the life history, ecology, and physiology of animals. Within a species, body size can vary substantially across space and time, and the mechanisms generating these patterns have been the focus of evolutionary and ecology research. 2. Bergmann’s Rule predicts a negative relationship between body size and temperature across the geographic range of endothermic animals; larger animals have a lower surface to volume ratio, which would allow for greater heat conservation. Despite the broad support for this pattern, its underlying mechanisms are heavily debated. Numerous alternative explanations have been proposed to explain why larger animals are found in colder climates, and vice versa, including heat dissipation, environmental seasonality, and resource availability. 3. We used the Pallid bat, Antrozous pallidus, as a model to evaluate Bergmannian size patterns and the relative support for major explanatory hypotheses of geographic body size variation. We tested the hypothesis that geographic size variation is predicted by productivity, as opposed to seasonality, heat conservation or dissipation, or some combination of these processes. Additionally, we investigated the potential ecomorphological consequences of size variation in Pallid bats by determining if skull shape (an indicator of bite performance) varies with size. 4. Whereas we did find that Pallid bat populations in northern latitudes are composed of larger individuals, our results suggest that net primary productivity and, to a lesser extent heat conservation, best explains size variation throughout the western range of this species. We also found that skull shape in Pallid bats changes in tandem with skull size, with larger bats having cranial traits associated with greater bite force production. 5. The results of our study indicate that variation in resource availability may be a key factor underlying spatial patterns in size, morphology and, possibly, feeding performance within wide-ranging bat species.1. 动物的体型与诸多生命史、生态学及生理学特征息息相关。同一物种内，体型会随空间与时间发生显著变化，而驱动这类体型变化的机制一直是进化生物学与生态学研究的核心议题。 2. 伯格曼法则（Bergmann’s Rule）预测：在恒温动物的地理分布范围内，体型与温度呈负相关关系——体型更大的动物拥有更低的表面积体积比，更利于维持体温。尽管该规律得到了大量研究支持，但其背后的作用机制仍存在广泛争议。学界已提出诸多替代假说，用以解释为何寒冷气候区的动物体型更大（反之亦然），其中包括散热假说、环境季节性假说以及资源可获得性假说。 3. 本研究以苍白蝙蝠（Pallid bat）*Antrozous pallidus*为模式物种，旨在验证伯格曼体型格局，并评估地理体型变异主要解释假说的相对支持强度。我们检验了“地理体型变异由生产力水平决定”这一假说，而非季节性、保温/散热机制，或是这些过程的共同作用。此外，我们通过探究头骨形状（咬合力表现的指示指标）是否随体型变化，分析了苍白蝙蝠体型变异可能带来的生态形态学后果。 4. 尽管我们确实发现高纬度地区的苍白蝙蝠种群个体体型更大，但研究结果表明，净初级生产力（net primary productivity）以及次要程度的保温机制，最能解释该物种西部分布范围内的体型变异。我们还发现，苍白蝙蝠的头骨形状会随头骨尺寸同步变化，体型更大的个体拥有与更高咬合力相关的颅骨特征。 5. 本研究结果表明，资源可获得性的差异可能是广布蝙蝠物种种群内体型、形态乃至取食表现空间格局形成的关键驱动因素。