Elevated heterozygosity clued atypical reproduction: evidence consistent with hybridogenesis mediating insular occurrence of a narrowly endemic spiny frog

Hybridogenesis is a rare reproductive mode found in interspecific hybrids that involves discarding one parental genome during gametogenesis and clonally transmitting the other, with the former renewed by backcrossing. It may in theory mediate species range expansion, since such hybrids can also cross and have pure-species offspring for establishing new populations and are often widespread probably due to hybrid vigor. Being inspired by a magnitude difference between estimates of individual heterozygosity, we collected genome-wide data and evaluated predictions from hybridogenesis of hybrids between the wide-ranging Asian spiny frog Quasipaa boulengeri and a narrow endemic, Q. robertingeri . We rejected other atypical modes of reproduction such as parthenogenesis or androgenesis and provided the first evidence consistent with a hypothesis that hybridogenesis mediated the occurrence of individuals far from the species range (~500 km). Despite contributing to early evidence of the only distinct hybridogenetic complex inferred in ten years, individual heterozygosity has likely been an often overlooked variable. The accumulating genome-wide data may serve as a resource for searching for individual heterozygosity clues of atypical reproduction of interspecific hybrid origin. The findings in spiny frogs make a case that genome-wide data provide crucial evidence for updating our knowledge on reproductive-mode evolution of taxa.