Leaf phenotypic variation in natural populations of Carpinus tschonoskii in China

Carpinus tschonoskii Maxim. exhibits rich leaf phenotypic variation and various leaf shapes, but few studies show why leaf phenotypic traits have such a large variation. Basic morphological markers may provide guidance for studying plant genetic variation and species protection and utilization. To study leaf phenotypic variations and the relationship between variation characteristics and climatic and geographical factors, phenotypic traits among natural populations were investigated. Results revealed that leaf phenotypes varied significantly among and within populations. Some populations had higher phenotypic diversity, while others had lower phenotypic diversity. Among the phenotypic traits, leaf area and petiole length had the most variation. Leaf index and primary lateral veins were the most stable phenotypes, which may be important reference indexes for phenotype identification in field investigations. There was a strong consistency between leaf phenotypic traits and geographical location. Plants in high latitudes tend to have longer leaves, and plants in low temperatures tend to have longer leaves and larger leaf perimeter. In addition, plants in areas with less rainfall have longer petioles. The 13 populations of C. tschonoskii can be divided into four branches by cluster analysis, and the results show a good relationship with the geographical location of each population. Additionally, some populations geographically isolated also had unique leaf phenotypes.