Striking diversity of male-killing symbionts and their mechanisms

Symbiosis is a fundamental characteristic of eukaryotic biology. Arthropods, including insects, often harbor maternally inherited endosymbiotic microbes, some of which have evolved the ability to selectively kill male hosts - a phenomenon known as 'male killing.' The evolutionary history and mechanisms of symbiont-induced male killing have remained poorly understood. However, recent studies have revealed a remarkable diversity of male-killing strategies and their associated causative genes in diverse bacteria and viruses that target different aspects of the host reproductive system. Some insects have evolved various suppressor genes to counteract male-killing actions. This review synthesizes the current knowledge on the evolution and mechanisms underlying microbe-induced male killing and explores their broader implications for the ecology and evolution of eukaryotic life forms.