Partial concordance between nuclear and organelle DNA in revealing the genetic divergence among Quercus glauca (Fagaceae) populations in Taiwan

Quercus glauca (Thunb. ex Murray) Oerst (Fagaceae) has a wide distributional range in Taiwan. In this study, the evolutionary history and the most genetically divergent sites of Q. glauca were studied using a nuclear gene marker, glyceraldehyde-3-phosphate dehydrogenase. Also, the consistency of the results obtained from nuclear gene and cytoplasmic loci was investigated. Using a genealogical approach (TCS software), we determined haplotypes and their relationships to one another. We used the level of divergence for each population from the remaining populations (calculated as mean values of pairwise population differentiation, F_ST, for each population) to locate the most genetically divergent areas in Taiwan. According to the average F _ST of each population in comparison with the remaining ones, a peak was found in the northern part of central Taiwan, and another was found in the southeastern region. The peak profiles of the mean F_ST values for all three DNA data sets (nDNA, cpDNA, and mtDNA) showed similar trends on both sides of the Central Mountain Ridge, except for the mtDNA sequence on the western side. This study suggests that two potential refugia existed in Taiwan during the last glaciation: one in the northern part of central Taiwan and another in southern Taiwan.