Histone H2A phylogeny. B. calyciflorus H2A sequences are shown in blue, bdelloid H2A sequences are shown in black. Phylogeny of canonical Histone H2A (purple), H2A.X (orange), and H2A.Z (green) based on 142 amino acid sequence alignment. Thickened branches indicate bootstrap support ≥ 70%. NCBI accession numbers for the sequences used in the alignment are given in the tree.