BACKGROUND Quantification of corolla shape variations helps biologists to investigate plant diversity and evolution. 3D images capture the genuine structure and provide comprehensive spatial information. RESULTS This study applied X-ray micro-computed tomography (µCT) to acquire 3D structures of the corollas of clade Corytholoma and extracted a set of 415 3D landmarks from each specimen. By applying the geometric morphometrics (GM) to the landmarks, the first 4 principal components (PCs) in the 3D shape and 3D form analyses, respectively, accounted for 87.86% and 96.34% of the total variance. The centroid sizes of the corollas only accounted for 5.46% of the corolla shape variation, suggesting that the evolutionary allometry was weak. The 4 morphological traits corresponding to the 4 shape PCs were defined as tube curvature, lobe area, tube dilation, and lobe recurvation. Tube curvature and tube dilation were strongly associated with the pollination type and contained phylogenetic signals in clade Corytholoma. The landmarks were further used to reconstruct corolla shapes at the ancestral states. CONCLUSIONS With the integration of µCT imaging into GM, the proposed approach boosted the precision in quantifying corolla traits and improved the understanding of the morphological traits corresponding to the pollination type, impact of size on shape variation, and evolution of corolla shape in clade Corytholoma.

中文翻译：

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表型变异，进化变构和花冠形状的祖先状态的3D揭示：进化枝花冠瘤（亚属Ligeriinae，Ge属科）的案例研究。

背景技术对花冠形状变化的定量帮助生物学家研究植物多样性和进化。3D图像捕获真正的结构并提供全面的空间信息。结果本研究应用X射线微计算机断层扫描（µCT）来获取分支性冠状动脉瘤花冠的3D结构，并从每个标本中提取出415个3D界标。通过对地标应用几何形态计量学（GM），以3D形状和3D形式进行分析的前4个主成分（PC）分别占总方差的87.86％和96.34％。花冠的质心大小仅占花冠形状变化的5.46％，这表明进化异体关系较弱。对应于4个形状PC的4个形态特征定义为管曲率，叶面积，扩张管，并切除叶。管弯曲和管扩张与授粉类型密切相关，并包含进化枝冠状动脉瘤的系统发生信号。地标还被用来重建祖先状态的花冠形状。结论通过将µCT成像技术整合到GM中，该方法提高了对花冠性状进行定量的精度，并增进了对与传粉类型，大小对形状变异的影响以及进化枝冠状花冠中花冠形状演变相对应的形态特征的了解。