Leaf morphological characteristics of section Quercus based on geometric morphometric analysis.

We conducted leaf geometric morphometric analysis (GMMs) for five Quercus species (Section Quercus) of Fagaceae. In total, 887 leaves chosen from 182 individuals of 20 natural popu-lations were marked with GMMs. Leaf morphological characteristics of these samples were digitized to visualize leaf morphological differences. Generalized Procrustes analysis could effectively exclude the influence of leaf position and size on leaf shape. Results of principal component analysis at tree-level showed that the leaf morphology of Q. dentata was different with Q. aliena and Q. serrata. Canonical variates analysis at tree-level showed that leaf morphology of Q. aliena could be accurately distinguished from the other four species in leaf symmetric components. The results of multivariate analysis of asymmetrical components in leaves showed no distinction among the five species. The analysis at leaf-level showed that the two groups with a higher degree of discrimination were Q. aliena vs. Q. dentata (99.5% vs. 100%) and Q. dentata vs. Q. serrata (99.0% vs. 100%), which could be accurately distinguished by leaf shape. The two groups with a slightly lower degree of discrimination were Q. fabri vs. Q. serrata (90.5% vs. 86.8%) and Q. dentata vs. Quercus mongolica (85.1% vs. 82.9%). Our results provided new insights for the leaf shape identification among species with frequent hybridization and introgression.