Figure 2.

Neighbor-joining trees of gene pairs. Neighbor-joining trees of gene pairs a) BMP8A/B, b) DDX19A/B and c) TUBG1/2 were created in MEGA3 using a Tamura-Nei model of sequence evolution. Opossum Bmp8, chicken Ddx19 and chicken Tubg were used as outgroups to root the trees. Bootstrap values (10,000 replicates) are shown on the interior branches of the tree. A distance scale is shown below each tree. Underlined species in a) are missing exon 1, preventing the use of this exon in the phylogenetic analysis (see Methods). Additionally, maximum likelihood trees were created for comparison and show highly similar patterns of evolution with the above trees [see Additional file 2].