The phylogenetic tree and functional dendrogram of Chinese Rhododendron species

Data processing methods and steps:A phylogeny comprising 442 Rhododendron species and three subspecies native to China, with the subspecies included as taxonomically similar to data-deficient species, was derived from the genus-level plastome phylogenetic tree of Mo et al. (unpubl. data), which was constructed using plastome sequences for 588 species (including 21 subspecies). To incorporate species lacking plastome sequences, we used a taxonomic similarity substitution approach, following the species description and classification system employed in FOC and/or the genus Rhododendron of China (Geng, 2014). Specifically, 137 species were inserted as polytomies with their morphologically closest relatives within the same subsection or section. Additionally, the remaining 24 species, which lacked clear morphological affinities or molecular data, were randomly inserted within their respective subsection or section in polytomies.To quantify the functional diversity of Rhododendron species in China, we collected seven key traits for each species: growth form (shrubs or trees), plant height, leaf length, leaf width, leaf texture (leathery, papery or membranous), number of flowers per inflorescence, and corolla length. These functional traits were compiled from FOC, the genus Rhododendron of China, and other relevant literature (see Table S1). For continuous traits, we utilized the maximum recorded value for each species. Based on these traits, we computed Gower’s distance matrix to quantify pairwise functional dissimilarity among the species (Pavoine et al., 2009). Subsequently, we constructed a functional dendrogram using hierarchical clustering with the unweighted pair group method with arithmetic mean (Wang et al., 2023).To investigate the relative contributions of environmental factors to the spatial patterns of Rhododendron diversity in China, we selected 18 environmental variables commonly used in macroecological studies. These variables were classified into six categories: energy, water, climatic seasonality, heterogeneity, human influence, and historical climate, representing contemporary climate conditions, habitat characteristics, human activities, and climatic stability since the Last Glacial Maximum.The detailed calculation methods for the diversity indices can be found in the Methods.Data description: The phylogenetic tree and functional dendrogram of Chinese Rhododendron species, the raw data used for their construction, and a table summarizing the 18 environmental variables and 15 diversity metrics.