Department of Evolutionary Biology, University of Vienna, Vienna, Austria.
KLI Institute for Evolution and Cognition Research, Klosterneuburg, Austria.
Syst Biol. 2020 Sep 1;69(5):913-926. doi: 10.1093/sysbio/syaa007.
It is a classic aim of quantitative and evolutionary biology to infer genetic architecture and potential evolutionary responses to selection from the variance-covariance structure of measured traits. But a meaningful genetic or developmental interpretation of raw covariances is difficult, and classic concepts of morphological integration do not directly apply to modern morphometric data. Here, we present a new morphometric strategy based on the comparison of morphological variation across different spatial scales. If anatomical elements vary completely independently, then their variance accumulates at larger scales or for structures composed of multiple elements: morphological variance would be a power function of spatial scale. Deviations from this pattern of "variational self-similarity" (serving as a null model of completely uncoordinated growth) indicate genetic or developmental coregulation of anatomical components. We present biometric strategies and R scripts for identifying patterns of coordination and compensation in the size and shape of composite anatomical structures. In an application to human cranial variation, we found that coordinated variation and positive correlations are prevalent for the size of cranial components, whereas their shape was dominated by compensatory variation, leading to strong canalization of cranial shape at larger scales. We propose that mechanically induced bone formation and remodeling are key mechanisms underlying compensatory variation in cranial shape. Such epigenetic coordination and compensation of growth are indispensable for stable, canalized development and may also foster the evolvability of complex anatomical structures by preserving spatial and functional integrity during genetic responses to selection.[Cranial shape; developmental canalization; evolvability; morphological integration; morphometrics; phenotypic variation; self-similarity.].
从测量特征的方差-协方差结构推断遗传结构和对选择的潜在进化反应，是定量和进化生物学的经典目标。但是，对原始协方差进行有意义的遗传或发育解释是困难的，经典的形态整合概念并不直接适用于现代形态计量数据。在这里，我们提出了一种新的形态计量策略，该策略基于不同空间尺度上的形态变化比较。如果解剖元素完全独立变化，那么它们的方差会在较大的尺度上积累，或者对于由多个元素组成的结构：形态方差将是空间尺度的幂函数。偏离这种“变异性自相似性”模式（作为完全不协调生长的零模型）表明解剖成分的遗传或发育共调节。我们提出了生物计量策略和 R 脚本，用于识别复合解剖结构的大小和形状的协调和补偿模式。在对人类颅骨变异的应用中，我们发现颅骨成分的大小存在协调变化和正相关，而其形状则由补偿变化主导，导致颅骨形状在较大尺度上的强烈通道化。我们提出，机械诱导的骨形成和重塑是颅骨形状补偿变化的关键机制。这种生长的表观遗传协调和补偿对于稳定、通道化的发育是必不可少的，并且通过在遗传对选择的反应过程中保持空间和功能的完整性，也可能促进复杂解剖结构的可进化性。
