Molecular Phylogenetic Inference And Biogeography In Fagus L.(Fagaceae)

Species of the genus Fagus L. are monoecious broad-leaved decious trees, which were also important constructive species in temperate forest in the Northern Hemisphere. Fagus species faver humid and temperate climate. In the Tertiary, they were widely distributed in all continents of the Northern Hemisphere, but at present disjunctly distributed in temperate areas of the Northern Hemisphere. Fagus is one of the most important groups in the study areas of Phylogeny, Evolution, Biogeography, Vegetation Ecology, Paleobotany, etc.. Now, there is no agreement for the classification, phylogenetic relationships and origin of the Fagus genus.Different scholars have different views. This paper analyzes the fagus genus in two aspects, the molecular phylogeny and the Panbiogeography, attmpts to discuss the question.In this study, we sampled7Fagus species and constructed molecular phylogenies of the genus based on three choroplast DNA regions (trnS-trnQtrnQ-rpsl6,trnT-trnL). Lithocarpus glaber, Quercus robur, Quercus rubra, Quercus baronii, Castanea mollissima were served as outgroups. The datasets were analyzed by Maximum parsimony (MP), Maximum likelihood (ML) and Bayesian inference (BI) analysis. The main result is that four groups were revealed in the phylogenetic tree, the plant taxa gathered together in terms of the regions as units(in North America, Japan, Europe, China). The consistency of the molecular phylogenetic classification system and the geographic distribution pattern, may indicate the great relevance between the formation and evolution of the Fagus speciese and the isolation differentiation led by the continent drift.In this paper, a panbiogeographical analysis of Fagus was undertaken in order to analyze the distribution pattern and evolution. Distribution data of581records of10species were obtained from herbaria and monograph. Track analysis of panbiogeography and software MartiTrack were used to analyze the data. Results of track analysis indicated that there is no the generalized track linking the distributions among China, Japan, Europe and North America or even China and Japan, two adjacent areas in East Asia. Two regional generalized tracks were only found within China and Japan. These facts imply that the Fagus distribution cannot be explained. Dispersal probably only occured in limited and/or local regions, and not as dispersal across the northern temperate zone in the Tertiary. The disjunction most likely resulted from,(1)geological historical events, such as Tethys westward movement, Qinghai-Tibet Plateau uplift, and Asian monsoon action,(2)climate change since the Tertiary, especially climate fluctuation during Quaternary glaciation; and Fagus biological characteristics with regard to humid, temperate climate, and annual rainfall. The results of the study of molecular phylogeny is consistent with the Panbiogeography result. This indicates that the process of formation and evolution of Fagus genus were affected by the continental drift and the geological history events.