Figure 1.
Phylogenetic tree illustrating the impact of using extraspecific and intraspecific calibration points.
The tree shows the locations of nucleotide changes (small vertical bars). The nucleotide changes within the study species represent segregating sites, some of which will be fixed in the long term, but most of which will be removed by drift or selection. The changes between the study species and outgroup species represent substitutions. If an estimate of the evolutionary rate is calibrated using an external calibration point, such as the split between the study and outgroup species, then the intraspecific rate will be underestimated. This will lead to an overestimation of times to divergence, including the age of the most recent common ancestor of the study species.
Table 1.
Divergence time estimates for conspecific phylogroups from 22 bird species
Figure 2.
Bayesian skyline plots showing the recent demographic history of bowhead whales, estimated using phylogenetic analysis of three alignments of the mitochondrial control region: (a) combined alignment of 68 modern haplotypes and 99 radiocarbon-dated, ancient DNA sequences; (b) modern sequences only; and (c) ancient sequences only.
All three plots are drawn to the vertical and horizontal scales.
Figure 3.
Maximum clade credibility tree from Bayesian analysis of mitochondrial control region sequences from 56 modern and 51 ancient brown bear samples, with a time scale calibrated using the radiocarbon dates of the ancient sequences.
Major clades and their geographic localities are given. Posterior probabilities are given for the nodes A-N, which are referred to in the text and in Table 2.
Table 2.
Bayesian age estimates for nodes labelled in Figure 3
Table 3.
Summary of estimates made using internal and external calibrations for the three data sets presented in this study