Principal component analysis has been used to test for similarities in ecology and life habit between modern and fossil birds; however, the two main portions of the hind limb—the foot and the long bone elements—have not been examined separately. We examine the potential links between morphology, ecology, and phylogeny through a synthesis of phylogenetic paleoecological methods and morphospace analysis. Both hind limb morphologies and species’ ecologies exhibit extreme phylogenetic clumping, although these patterns are at least partially explainable by a Brownian motion style of evolution. Some morphologies are strongly correlated with particular ecologies, while some ecologies are occupied by a variety of morphologies. Within the morphospace analyses, the length of the hallux (toe I) is the most defining characteristic of the entire hind limb. The foot and hind limb are represented on different axes when all measurements are considered in an analysis, suggesting that these structures undergo morphological change separately from each other. Early birds tend to cluster together, representing an unspecialized basal foot morphotype and a hind limb reliant on hip-driven, not knee-driven, locomotion. Direct links between morphology, ecology, and phylogeny are unclear and complicated and may be biased due to sample size (~60 species). This study should be treated as a preliminary analysis that further studies, especially those examining the vast diversity of modern birds, can build upon.

中文翻译：

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鸟类后肢足部形态学主成分分析及生态学与系统发育关系

主成分分析已被用于检验现代鸟类与化石鸟类在生态学和生活习性方面的相似性；然而，后肢的两个主要部分——足部和长骨元件——尚未单独检查。我们通过综合系统发育古生态学方法和形态空间分析来检查形态学、生态学和系统发育之间的潜在联系。后肢形态和物种的生态学都表现出极端的系统发育聚集，尽管这些模式至少可以部分地用布朗运动的进化方式来解释。一些形态与特定生态密切相关，而一些生态则被多种形态所占据。在形态空间分析中，拇趾（脚趾 I）的长度是整个后肢最明确的特征。当在分析中考虑所有测量值时，脚和后肢在不同的轴上表示，这表明这些结构彼此分开经历形态变化。早起的鸟类倾向于聚集在一起，代表一种非特化的基足形态类型和一种依赖于髋部驱动而非膝部驱动的运动的后肢。形态学、生态学和系统发育之间的直接联系尚不清楚且复杂，并且可能由于样本量（约 60 个物种）而存在偏差。这项研究应被视为一项初步分析，进一步的研究，特别是那些检查现代鸟类的巨大多样性的研究，可以建立在此基础上。早起的鸟类倾向于聚集在一起，代表一种非特化的基足形态类型和一种依赖于髋部驱动而非膝部驱动的运动的后肢。形态学、生态学和系统发育之间的直接联系尚不清楚且复杂，并且可能由于样本量（约 60 个物种）而存在偏差。这项研究应被视为一项初步分析，进一步的研究，特别是那些检查现代鸟类的巨大多样性的研究，可以建立在此基础上。早起的鸟类倾向于聚集在一起，代表一种非特化的基足形态类型和一种依赖于髋部驱动而非膝部驱动的运动的后肢。形态学、生态学和系统发育之间的直接联系尚不清楚且复杂，并且可能由于样本量（约 60 个物种）而存在偏差。这项研究应被视为一项初步分析，进一步的研究，特别是那些检查现代鸟类的巨大多样性的研究，可以建立在此基础上。