Significance

The evolution of asexuality is thought to be prevented when males play a critical role beyond that of gamete provision. We demonstrated high numbers of neo-sex chromosomes and enhanced heterozygosity in males of the termite Glyptotermes nakajimai , which appears to compensate for inbreeding within termite colonies. Furthermore, we showed that two asexual G . nakajimai lineages have evolved via independent intraspecific hybridizations between sexual lineages with differing diploid chromosome numbers. This has resulted in markedly higher levels of heterozygosity of females than males in the sexual lineage. Our study illustrates that asexual females may replace the role of males in maintaining heterozygosity, implying a route to the evolution of asexuality.