The phylogenetic tree inferred from rbcL sequences under the UCLD model. Geologic timescale is tagged above the phylogenetic tree (Unit: Million years). The estimated global atmospheric CO2 concentrations from the GEOCARB III model are mapped under the phylogenetic tree according to the geologic timeline. Each node in the tree is numbered. Posterior probability values are shown along the branches and those with posterior probability ≥ 0.9 are heavily thickened. Two time intervals are demonstrated in grey. The six major clades concerned in this research are indicated: Podocarpaceae, Podocarpus I and II, Cephalotaxaceae, Taxus and Torreya. The length of each branch is in proportion to the divergence time estimated by using the UCLD model.