Data from: Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis

Flight capacity is one of the most important innovations in animal
evolution; it only evolved in insects, birds, mammals and the extinct
pterodactyls. Given that powered flight represents a demanding aerobic
activity, an efficient cardiovascular system is essential for the
continuous delivery of oxygen to the pectoral muscles during flight. It is
well known that the limiting step in the circulation is stroke volume (the
volume of blood pumped from the ventricle to the body during each beat),
which is determined by the size of the ventricle. Thus, the fresh mass of
the heart represents a simple and repeatable anatomic measure of aerobic
power of an animal. Although several authors have already compared heart
masses across bird species, a phylogenetic comparative analysis of these
comparisons is still lacking. Compiling heart sizes for 915 species and
applying several statistical procedures controlling for body size and/or
testing for adaptive trends in the dataset (e.g., model selection
approaches, phylogenetic generalized linear models), we found that
(residuals of) heart sizes are consistently associated with four
categories of flight capacity. In general, our results indicate that
species exhibiting continuous hovering flight (i.e., hummingbirds) have
substantially larger hearts than do other groups, that species that use
flapping flight and gliding show intermediate values, and that species
categorized as poor flyers show the smallest values. Our study shows that
at a broad scale, routine flight modes seem to have shaped the energetic
requirements of birds sufficiently to be anatomically detected at the
comparative level.

飞行能力是动物演化历程中最为重要的革新之一，该性状仅在昆虫、鸟类、哺乳类以及已灭绝的翼龙类中演化形成。鉴于动力飞行属于高强度有氧代谢活动，高效的心血管系统对于飞行过程中持续向胸肌输送氧气至关重要。众所周知，血液循环的限制性步骤为每搏输出量（stroke volume）——即每一次心跳时心室泵入体循环的血液容积——其大小由心室尺寸决定。因此，心脏鲜重是衡量动物有氧代谢能力的一种简便且可重复的解剖学指标。尽管已有诸多学者针对不同鸟类的心脏重量开展过比较研究，但目前仍缺乏针对此类研究开展的系统发育比较分析。本研究整合了915个物种的心脏尺寸数据，并采用多种统计方法控制体型效应、检验数据集内的适应性演化趋势（如模型选择方法、系统发育广义线性模型），结果发现心脏尺寸的（残差）始终与四类飞行能力类别显著相关。总体而言，本研究结果显示：持续悬停飞行的类群（如蜂鸟）的心脏尺寸显著大于其他类群；使用振翅飞行与滑翔的类群心脏尺寸处于中等水平；而被归类为飞行能力较弱的类群心脏尺寸最小。本研究表明，在宏观尺度上，日常飞行模式已足够塑造鸟类的能量代谢需求，使得该特征能够在比较解剖学层面被检测到。