INCREASED MALE-FERTILITY IN TRIBOLIUM-CONFUSUM BEETLES AFTER INFECTION WITH THE INTRACELLULAR PARASITE WOLBACHIA

THE cytoplasmically inherited microorganism Wolbachia pipientis behave s like a sexually selected trait in its host, the flour beetle Triboli um confusum, enhancing male fertility at the expense of female fecundi ty. Here we show that infected females have fewer offspring than uninf ected females but infected males have a large fertility advantage over uninfected males within multiply-inseminated infected or uninfected f emales. The male fertility effect accelerates the spread of the Wolbac hia through the host population and expands the initial opportunity fo r hitch-hiking of host nuclear genes. Sperm competition in a host, med iated by endosymbionts, has not been previously described.