REPRODUCTIVE INTERFERENCE. “Both incompatibility and parthenogenesis microorganisms alter host chromosome behaviour during early mitotic divisions of the egg. Incompatibility bacteria act by interfering with paternal chromosome incorporation in fertilized eggs, whereas parthenogenesis bacteria prevent segregation of chromosomes in unfertilized eggs. These traits are adaptive for the microorganisms.”
http://www.nature.com/nature/journal/v361/n6407/abs/361066a0.html