Fig. 1

Evolutionary relationships of the ABCG2 and ABCG2-like genes in birds. The phylogenetic tree was constructed with the ML method using MEGA7 software. The numbers on the nodes represent the bootstrap support. The outermost ring contains the Latin name and gene name of the birds and outgroup species, and ABCG2-like is abbreviated as ABCG2-L. The red circles indicate the birds whose ABCG2-like genes were lost