Two male-killing from that are closely related but distinct in genome structure.

Insects harbour diverse maternally inherited bacteria and viruses, some of which have evolved to kill the male progeny of their hosts (male killing: MK). The fly species carries a maternally transmitted MK-inducing partiti-like virus, but it was unknown if it carries other MK-inducing endosymbionts. Here, we identified two male-killing strains (Biau1 and Biau2) from and compared their genomes to elucidate their evolutionary processes. The two strains were genetically closely related but had exceptionally different genome structures with considerable rearrangements compared with combinations of other strains. Despite substantial changes in the genome structure, the two strains did not experience gene losses that would disrupt the male-killing expression or persistence in the host population. The two -infected matrilines carried distinct mitochondrial haplotypes, suggesting that Biau1 and Biau2 have invaded independently and undergone considerable genome changes owing to unknown selective pressures in evolutionary history. This study demonstrated the presence of three male-killers from two distinct origins in one fly species and highlighted the diverse and rapid genome evolution of MK in the host.