Leaf phenotypic variation in natural populations of the Cunninghamia securinega at different altitudes

To reveal the leaf phenotypic diversity and its variation pattern in the natural Cunninghamia securinega population at different altitude gradients, to study the correlation between leaf phenotypic traits and altitude climate, and to provide scientific basis for the collection, conservation and utilization of the C. securinega germplasm resources.

Twelve leaf phenotypic traits from four natural C. securinega populations at different altitudes were investigated in Xiangxi National Nature Reserve, Hunan province by using nested ANOVA, correlation analysis, principal component analysis and cluster analysis.

Except for leaf width, 11 leaf phenotypic traits were significantly (P < 0.05) or highly significantly (P < 0.01) different between and within populations, with rich variation; The overall variation in leaf phenotypes among natural populations showed a decreasing trend with increasing altitude, and the populations with the highest and lowest coefficients of variation were Pop1 (18.52%) and Pop4 (13.95%), respectively; The intra-population phenotypic differentiation coefficient (77.46%) was greater than the inter-population phenotypic differentiation coefficient (22.54%), indicating that intra-population variation was the main source of variation, and the degree of population differentiation was at a low to medium level. The correlation analysis showed that needle thickness, specific leaf area, and specific leaf mass showed highly significantly negative correlations with temperature (P < 0.001) and positive correlations with precipitation (P < 0.001) as elevation increased, which suggested that the needles of hemlock exhibit stress tolerance strategies in order to adapt to the environment. Using the Ward.D2 hierarchical clustering method to analyze the clustering of the C. securinega populations, the four natural populations of the C. securinega at different elevations could be divided into four taxa.

The overall leaf phenotypic diversity of the C. securinega population showed a decreasing trend with increasing altitude and was significantly correlated with the altitude-climate factors. The phenotypic variation between and within populations was rich, but intra-population variation was dominant.