Geometric morphometric analyses of leaf shapes in two sympatric Chinese oaks: Quercus dentata Thunberg and Quercus aliena Blume (Fagaceae)
Geometric morphometric analyses (GMMs) of the leaf shape can distinguish two congeneric oak species Quercus dentata Thunberg and Quercus aliena Blume in sympatric areas.
High genetic and morphological variation in different Quercus species hinder efforts to distinguish them. In China, Q. dentata and Q. aliena are generally sympatrically distributed in warm temperate forests, and share some leaf morphological characteristics.
The aim of this study was to use the morphometric methods to discriminate these sympatric Chinese oaks preliminarily identified from molecular markers.
Three hundred sixty-seven trees of seven sympatric Q. dentata and Q. aliena populations were genetically assigned to one of the two species or hybrids using Bayesian clustering analysis based on nSSR. This grouping served as a priori classification of the trees. Shapes of 1835 leaves from the 367 trees were analyzed in terms of 13 characters (landmarks) by GMMs. Correlations between environmental and leaf morphology parameters were studied using linear regression analyses.
The two species were efficiently discriminated by the leaf morphology analyses (96.9 and 95.9% of sampled Q. aliena trees and Q. dentata trees were correctly identified), while putative hybrids between the two species were found to be morphologically intermediate. Moreover, we demonstrated that the leaf morphological variations of Q. aliena, Q. dentata, and their putative hybrids are correlated with environmental factors, possibly because the variation of leaf morphology is part of the response to different habitats and environmental disturbances.
GMMs were able to correctly classify individuals from the two species preliminary identified as Q. dentata or Q. aliena by nSSR. The high degree of classification accuracy provided by this approach may be exploited to discriminate other problematic species and highlight its utility in plant ecology and evolution studies.
KeywordsGeometric morphometrics Genetic assignment Leaf morphology Quercus Sympatric distribution
We thank anonymous reviewers for helpful comments on a previous version of this manuscript. We thank Dr. Antoine Kremer of INRA, France; Saneyoshi Ueno of Forestry and Forest Products Research Institute, Japan; and Dr. Nian Wang of Shandong Agricultural University, China, for the improvement of the manuscript. We would also like to thank Dr. Juqing Kang of Shanxi Normal University and Shangfang Mountain National Forest Park, Beijing, P.R. China, for assisting us during the field sampling.
This research was supported by the Fundamental Research Funds for the Central Universities (grant no. 2015ZCQ-LX-03), the National Science Foundation of China (grant no. 41671039), and the Beijing Nova Program for FKD (grant no. Z151100000315056).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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