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. 2023 May 26;132(1):61–76. doi: 10.1093/aob/mcad069

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© The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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Fig. 2. — Multivariate cluster analysis of floral traits. (A) Principal component analysis (PCA) of 17 floral traits across 29 species. Data points represent single flowers (N = 309) coloured by k-means cluster with ad hoc assignment of flower morphology (top left), with symbols representing the pollination mode (bottom left); representative flowers are shown for each of five k-means clusters. Principal component (PC)1 (as a percentage of total variance explained) discriminates flowers mostly by sexual system, segregating dioecious, wind-pollinated taxa (at both extremes of the axis) from hermaphrodites (H) comprising all three pollination modes at the centre of the axis. PC3 separates the central hermaphroditic flower cluster further into three morphotypes, interpreted as petaloid sepals, showy stamens and an intermediate morph, separating insect-pollinated species at its extremes from mixed-pollinated taxa towards the centre. Filled symbols identify species with field-validated pollination mode data. (B) Biplot corresponding to the PCA shown in panel A, with loadings for the different floral traits represented as arrows towards larger values; the direction of the arrows indicates the contribution of each trait to the respective PC. (C) Top: phylogenetic PCA (pPCA) of flower morphology in Thalictrum (Ranunculaceae). The dataset (from panel A) uses species averages, with species names abbreviated to the first three letters. K-means analysis resulted in three clusters (k = 3), enclosed in dashed lines, and the available pollination mode information is shown with filled shapes as in panel A; colour-coding is as in panel D. Bottom: PC combination from panel A that best matches the pPCA outcome (PC1 vs. PC2), for a direct comparison, showing a continuum of flower morphotypes and pollination modes along PC2. (D) Ancestral state reconstruction of flower morphotypes for 29 Thalictrum species from multivariate analysis shown in panel A. The first three categories correspond to hermaphroditic sexual systems, while the last two encompass dioecy, andromonoecy and cryptic dioecy (T. pubescens), respectively. Clades A–C are as in Fig. 1. Pie charts represent the marginal probability of observing a certain flower morphotype (character state) at any given node.