Tree Genetics & Genomes

, Volume 10, Issue 4, pp 989–999

Genetic admixing of two evergreen oaks, Quercus acuta and Q. sessilifolia (subgenus Cyclobalanopsis), is the result of interspecific introgressive hybridization


    • Gifu Academy of Forest Science and Culture
  • Megumi Okada
    • Gifu Academy of Forest Science and Culture
Original Paper

DOI: 10.1007/s11295-014-0737-x

Cite this article as:
Tamaki, I. & Okada, M. Tree Genetics & Genomes (2014) 10: 989. doi:10.1007/s11295-014-0737-x


In forests worldwide, Quercus is a major genus; however, the boundaries between the constituent species are relatively weak, and hybridization is reported frequently. In this study, we examined Quercus acuta and Quercus sessilifolia (subgenus Cyclobalanopsis), which have a putative hybrid—Q. x takaoyamensis. We investigated leaf morphological traits and microsatellites of Q. acuta and Q. sessilifolia in the area where the two species are both found. Although the leaf traits overlapped, the two species could be distinguished morphologically as demonstrated by principal component analysis based on a range of these traits. They were also genetically differentiated, with F ST = 0.104. However, they shared most of the alleles at all eight loci examined, and considerable genetic admixing was detected. Admixture analysis demonstrated that Q. acuta and Q. sessilifolia, respectively, contained 11 and 24 % of individuals with a probability of less than 0.9 of being correctly assigned to their species. Model-based testing showed that this admixing was created by not only shared ancestral polymorphism but also by hybridization. Effective population size and migration rate were estimated using the coalescent approach. We estimated 8.843 and 71.98 effective numbers of migrants per generation to Q. acuta and Q. sessilifolia, respectively. Theoretically, one to ten migrants per generation are required to prevent complete genetic differentiation. Based on the results of this study, it appears that genetic admixing, with sharing of most alleles, is probably common in the two species and is maintained by interspecific introgressive hybridization.


Migration rate Leaf shape Introgression Effective number of migrants Genetic admixture Coalescent approach

Supplementary material

11295_2014_737_MOESM1_ESM.pdf (166 kb)
ESM 1 (PDF 166 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2014