Morphological Variation And Population Genetic Research In Two Sympatric Quercus

The species determination especially for the closely related species is the first and foremost steps in forest resources study.Quercus(Fagaceae)is a phylogenetically complex genus,and also a model organisms in the development of ecological species concepts.Two closely related oaks Q.dentata Thunb.and Q.aliena BI.,are widely distributed in China,with great economic and the ecological value.In the thesis,451 trees of six sympatric Q.dentata and Q.aliena populations were analyzed based on 12 SSR markers.STRUCTURE analysis revealed that 451 individuals were clearly divided into two clusters with different genotype and there existed wide and asymmetric gene flow between the two species.239 individuals were determined as Q.aliena,154 individuals were determined as Q.dentata,and 58 individuals were determined as hybrids when Q≥ 0.9 were considered to be pure species and the others were considered to be hybrids.The observed heterozygosity was 0.64 and 0.63 within the Q.dentata and Q.aliena respectively and the expected heterozygosity was 0.61 within two species,which showed a high level of genetic diversity within the two species.The genetic diversity(FST)between the two species was 0.108,indicating a middle level of genetic differentiation.Geometric morphometric analysis was conducted basing on 1835 leaves of 367 individuals.At leaf level,the Principal Component Analysis(PCA)results showed that significant leaf differences between Q.dentata and Q.aliena,and the hybrids were scattered.At individual level,95.90 and 96.88%of Q.aliena and Q.dentata could be accurately distinguished according to Discriminant Analysis(DA);Canonical Variate Analysis(CVA)results showed that the leaf morphology of the hybrids were mainly located between the leaf shape of Q.aliena and Q.dentata,and were closer to the Q.aliena;Two Blocks Partial Least Squares(2B-PLS)was performed to analysis the symmetric and asymmetric components onto leaf size,results showed that significant allometric patterns of symmetric components variation were detected,however no significant allometry was detected on asymmetric components.Linear-regression Analysis were used to study the relationships between the relative leaf infactors(symmetric and asymmetric components,size)and environment variables.The result showed that there were significant effect of the environment variables to leaf shape and size.Integrating molecular marker and morphological marker analysis,the Q.aliena and Q.dentata can be distinguished clearly in both methods.In addition,the thesis revealed there existed a wide range of gene flow and hybrids within sympatric population Q.aliena and Q.dentata.The hybridized individuals were mostly located between the leaves of Q.aliena and Q.dentata,however some of the hybrids were indistinguishable from morphology.