Leaf phenotypic variation of endangered plant Tetracentron sinense Oliv. and influence of geographical and climatic factors

To analyze the degree and pattern of phenotypic variation in leaves of Tetracentron sinense Oliv from the perspective of genetic and environmental adaptation and thus contribute to effective evidence-based conservation and management strategies for germplasm resources, we measured 17 morphological and epidermal micromorphological leaf traits from 24 natural populations of T. sinense. Nested analysis of variance, multiple comparison, principal component analysis (PCA), cluster analysis, and correlation analysis were used to explore phenotypic leaf variation among and within populations and potential correlations with geographic and environmental factors. There were significant differences in 17 leaf phenotypic traits among and within populations. The mean phenotypic differentiation coefficient of the 17 traits was 56.34%, and the variation among populations (36.4%) was greater than that within populations (27.2%). The coefficient of variation (CV) of each trait ranged from 4.6 to 23.8%, and the mean was 11.8%. Phenotypic variation of leaves was related to environmental factors such as average annual sunshine hours, average July temperature, and average annual rainfall. The variation changed along gradients of longitude, latitude, and altitude. The PCA clustered the 24 natural populations into four groups. Our study suggests that phenotypic variation in T. sinense occurred primarily among populations, with moderate levels of phenotypic differentiation among populations and low levels of phenotypic variation within populations. The plant’s poor adaptability to the environment is likely an important contributor to its endangerment. Accordingly, conservation strategies are proposed to protect and manage the natural populations of T. sinense.