Persistence of an unusual triple sex chromosome system through allopolyploidization in African clawed frogs (Xenopus, subgenus Silurana)

African clawed frogs (Xenopus) have a high rate of genome duplication, which may catalyze evolution-including of sex chromosomes. To explore this, for each of four species in the subgenus Silurana, we analyzed sex-associated genetic variation, and in the diploid species X. tropicalis we explored population structure. We found that the sex-linked regions in all four species are homologous, and we infer that X. calcaratus has an unusual sex …