Behavior ofWolbachiaEndosymbionts FromDrosophila SimulansinDrosophila Serrata, A Novel Host

Many species harbor the incompatibility‐inducing microbeWolbachia, a maternally inherited endoparasite that causes reduced egg hatch in crosses between infected males and uninfected females. Infected females are immune to this effect, which gives them a relative fitness advantage that results in the spread of the infection. The strength of incompatibility, fitness deficits associated with the infection, and transmission rate from mother to offspring largely determine the rate and extent of spread ofWolbachiain a population. We transferredWolbachiafromDrosophilasimulans toDrosophila serrata, a novel host, and compared parameter estimates with those from three naturally occurringDrosophila‐Wolbachiaassociations believed to be of different ages. TransfectedD. serratashowed strong incompatibility, low transmission efficiency, and an associated fitness deficit, and they would probably be unable to spread in nature. The comparisons generally supported the predicted evolution of a host‐Wolbachiaassociation. The parameters peculiar to any given host‐Wolbachiaassociation may determine whether the microbial strain can spread in that host.