The COI (CO1, COX1) gene, encoding the cytochrome c oxidase subunit 1 (cox1), is one of 13 protein-coding genes in vertebrate mitochondria. The gene has often been used to infer phylogenetic relationships. In the matrix below, homologous bases of the COI gene of a number of selected species are aligned to identify cases of convergent (yellow) vs. apomorphic (red) base substitutions.        

Most base substitutions are found in the third codon position without accompanying changes of amino-acid composition. Those base substitutions that lead to an exchange of the encoded amino acid are marked in the following table, with singeltons highlighted in orange, cases of convergent evolution highlighted in yellow, and apomorphies highlighted in red: 

Derived amino-acid evaluation matrix of the COI gene of selected species of Galloanserae. Yellow highlighting indicates convergencies, orange highlighting indicates singletons, and red highlighting indicates apomorphies. Finally, black highlighting indicates sites where Galliformes and Anseriformes differ in base composition.  

The following graphic provides an overview of the identified apomorphic base-substitutions of the COI gene of selectes species of Galloanserae: 

"COI apotree" showing apomorphic/apogenic DNA-base substitutions in the COI gene of selected taxa of Galloanserae. Base changes that are highlighted in light blue indicate cases where the base changes are accompanied by a change of the encoded amino acids. Note that the phylogenetic position of Biziura lobata has not been established yet.