Mitochondrial gene orders in ardeid birds. Only the region between the Cytb and 12S rRNA is shown. A: duplicate tRNAThr–CR gene order; B: duplicate CR gene order; C: duplicate tRNAGlu–CR gene order; D: duplicate tRNAThr–tRNAPro and CR gene order. The gene order names follow the description by Gibb et al. . pCytb: partial Cytb. ψ: pseudo gene.