Molecular Phylogeny And Biogeography Of Cedrus

Mountain regions between the fortieth parallels of latitude are attractive to biogeographers due to their importance in the survival of many plant species during Ice Ages. It is of great interest to investigate the floristic relationship between the Mediterranean and the Tibetan plateau, two world hotspots of biodiversity. Here the phylogeny of Cedrus (true cedars), a genus comprising four species with a disjunct distribution in the Mediterranean region and western Himalaya, was constructed based on sequence analysis of eight cp- and mtDNA fragments paternally and maternally inherited, respectively. Then, the vicariance and dispersal of the true cedars during the Tertiary were discussed. The main results are summarized as follows:No intraspecific sequence variation was detected from the five cpDNA fragments ( psbB-psbH, rpL16 intron, 5'rps12-rpL20, trnC-trnD, trnT-trnF) and the three mtDNA regions (nad1 intron 2, nad5 intron 1, orf25) we analyzed. Phylogenetic analyses using three combined DNA datasets (5 chloroplast, 3 mitochondrial and 8 cytoplasmic fragments) yielded the most parsimonious trees with the same topology that the Himalayan cedar C. deodara has a basal position and the North African species C. atlantica is sister to a clade comprising C. libani and C. brevifolia, two species from the eastern Mediterranean area. This result was consistent with previous cytological and biochemical analyses.From the beginning of Tertiary, the global climate changed from extremes of expansive warmth with ice-free poles to extremes of cold with massive continental ice-sheets and polar ice caps. The climatic oscillation provided opportunities for biota dispersal and subdivision.