Phylogenetic relationships and divergence times of the family Araucariaceae based on the DNA sequences of eight genes

Araucariaceae is one of the most primitive families of the living conifers, and its phylogenetic relationships and divergence times are critically important issues. The DNA sequences of 8 genes, i.e., nuclear ribosomal 18S and 26S rRNA, chloroplast 16S rRNA, rbcL, matK and rps4, and mitochondrial coxI and atp1, obtained from this study and GenBank were used for constructing the molecular phylogenetic trees of Araucariaceae, indicating that the phylogenetic relationships among the three genera of this family should be ((Wollemia, Agathis), Araucaria). On the basis of the fossil calibrations of Wollemia and the two tribes Araucaria and Eutacta of the genus Araucaria, the divergence time of Araucariaceae was estimated to be (308 ± 53) million years ago, that is, the origin of the family was in the Late Carboniferous rather than Triassic as a traditional view. With the same gene combination, the divergence times of the genera Araucaria and Agathis were (246 ± 47) and (61 ± 15) Ma, respectively. Statistical analyses on the phylogenetic trees generated by using different genes and comparisons of the divergence times estimated by using those genes suggested that the chloroplast matK and rps4 genes are most suitable for investigating the phylogenetic relationships and divergence times of the family Araucariaceae. Supported by the National Infrastructure of Natural Resources for Science and Technology (Grant No. 2005DKA21403), MOST Basic Science and Technology (Grant No. 2007FY110100), Shanghai Leading Academic Discipline Project (Grant No. B111), Shanghai Science and Technology Committee (Grant No. 07XD14025), the Graduate Students Innovation Foundation of Fudan University (Grant No. EYH1322098) and National Science Fund for Fostering Talents in Basic Science (Grant No. J0630643)