Supporting data for "3D revelation of phenotypic variation, evolutionary allometry, and ancestral states of corolla shape: a case study of clade Corytholoma (subtribe Ligeriinae, family Gesneriaceae)"

Quantification of corolla shape variations helps biologists to investigate the diversity and evolution in plants. This study applied X-ray micro-computed tomography (µCT) to acquire three-dimensional (3D) structures of the corollas of clade Corytholoma. After acquiring volumetric images of the corollas and extracting a set of 415 3D landmarks from each volumetric image, the major 3D shape and 3D form variations of the corollas were identified from the landmarks by using geometric morphometrics (GM). Evolutionary allometry of the corolla shape was assessed. Morphological traits corresponding to the major shape variations were also defined and quantified and were subsequently used to examine their association with pollination type and to evaluate the phylogenetic signals. The landmarks were further used to reconstruct corolla shapes at the ancestral states.<br>GM results revealed that the first four 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 four morphological traits corresponding to the four 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.<br>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.

花冠形状变异的量化研究，有助于生物学家探究植物的多样性与演化历程。本研究采用X射线显微计算机断层扫描（X-ray micro-computed tomography，µCT）技术，获取了Corytholoma演化支植物花冠的三维（3D）结构。在获取花冠的容积影像并从每幅影像中提取415个三维标志点（3D landmarks）后，本研究借助几何形态测量学（geometric morphometrics，GM）方法，从这些标志点中识别出花冠主要的三维形状与三维形态变异。本研究对花冠形状的进化异速生长关系进行了评估，同时针对与主要形状变异对应的形态性状完成定义与量化，进而利用这些性状分析其与传粉类型的关联，并评估系统发育信号（phylogenetic signals）。此外，研究人员还借助这些标志点重构了祖先状态下的花冠形状。
几何形态测量学（GM）分析结果显示，三维形状与三维形态分析中，前四个主成分（principal components，PCs）分别解释了总变异的87.86%与96.34%。花冠的质心尺寸仅解释了5.46%的花冠形状变异，表明进化异速生长关系较弱。与四个形状主成分对应的四个形态性状分别被定义为：花冠管曲率、裂片面积、花冠管扩张度以及裂片反曲度。其中，花冠管曲率与花冠管扩张度与传粉类型显著相关，且在Corytholoma演化支中存在系统发育信号。
通过将X射线显微计算机断层扫描成像与几何形态测量学相结合，本研究提出的方法提升了花冠性状量化的精度，同时加深了学界对Corytholoma演化支中与传粉类型相关的形态性状、体型对形状变异的影响以及花冠形状演化历程的认知。