Relic of ancient recombinations in gibbon ABO blood group genes deciphered through phylogenetic network analysis

The primate ABO blood group gene encodes a glycosyl transferase (either A or B type), and is known to have large coalescence times among the allelic lineages in human. We determined nucleotide sequences of ca. 2.2 kb of this gene for 23 individuals of three gibbon species (agile gibbon, white-handed gibbon, and siamang), and observed a total of 24 haplotypes. We found relics of five ancient intragenic recombinations, occurred during ca. 2–7 million years ago, through a phylogenetic network analysis. The coalescence time between A and B alleles estimate precede the divergence (ca. 8 MYA) of siamang and common gibbon lineages. This establishes the coexistence of divergent allelic lineages of the ABO blood group gene for a long period in the ancestral gibbon species, and strengthens the non-neutral evolution for this gene.