Table_S3_p_values_pairwise_correlation_all_chars.txt from Computational biomechanics changes our view on insect head evolution

Despite large-scale molecular attempts, the relationships of the basal winged insect lineages dragonflies, mayflies and neopterans, are still unresolved. Other data sources, such as morphology, suffer from unclear functional dependencies of the structures considered, which might mislead phylogenetic inference. Here, we assess this problem by combining for the first time biomechanics with phylogenetics using two advanced engineering techniques, multibody dynamics analysis and finite-element analysis, to objectively identify functional linkages in insect head structures which have been used traditionally to argue basal winged insect relationships. With a biomechanical model of unprecedented detail, we are able to investigate the mechanics of morphological characters under biologically realistic load, i.e. biting. We show that a range of head characters, mainly ridges, endoskeletal elements and joints, are indeed mechanically linked to each other. An analysis of character state correlation in a morphological data matrix focused on head characters shows a highly significant correlation of these mechanically linked structures. Phylogenetic tree reconstruction under different data exclusion schemes based on the correlation analysis unambiguously supports a sistergroup relationship of dragonflies and mayflies. The combination of biomechanics and phylogenetics as it is proposed here could be a promising approach to assess functional dependencies in many organisms to increase our understanding of phenotypic evolution.

尽管已有大量基于分子手段的研究，但基部有翅昆虫支系（basal winged insect lineages）——蜻蜓（dragonflies）、蜉蝣（mayflies）以及新翅类（neopterans）——之间的系统发育关系仍未明确。诸如形态学（morphology）这类其他数据来源，由于所涉结构的功能关联尚不明确，可能会误导系统发育推断（phylogenetic inference）。本研究首次将生物力学（biomechanics）与系统发育学（phylogenetics）相结合，采用多体动力学分析（multibody dynamics analysis）与有限元分析（finite-element analysis）这两种先进工程技术，客观识别出传统上用于论证基部有翅昆虫类群关系的昆虫头部结构的功能关联。借助前所未有的精细化生物力学模型，我们能够在符合生物学现实的载荷（load）条件下（即取食咬合），对形态学特征（morphological characters）的力学机制开展研究。研究表明，一系列头部特征——主要包括脊突、内骨骼结构（endoskeletal elements）以及关节——确实存在力学上的相互关联。针对以头部特征为核心的形态学数据矩阵（data matrix）开展的性状状态相关性分析（character state correlation analysis）显示，这些存在力学关联的结构呈现出极高的显著相关性。基于相关性分析设置的不同数据排除方案下的系统发育树重建（phylogenetic tree reconstruction）结果，明确支持蜻蜓与蜉蝣互为姊妹群（sistergroup）的系统发育关系。本研究提出的生物力学与系统发育学结合的研究范式，有望成为评估众多生物类群功能关联的有效手段，从而加深我们对表型演化（phenotypic evolution）的认知。