Host nuclear genotype influences phenotype of a conditional mutualist symbiont

Arthropods commonly carry maternally-inherited intracellular bacterial symbionts that may profoundly influence host biology and evolution. The intracellular symbiont Rickettsia sp. nr. bellii swept rapidly into populations of the sweetpotato whitefly Bemisia tabaci in the southwestern USA. Previous laboratory experiments showed female-bias and fitness benefits were associated with Rickettsia infection, potentially explaining the high frequencies of infection observed in field populations, but the effects varied with whitefly genetic line. Here we explored whether host extranuclear or nuclear genes influenced the variation in the Rickettsia-host phenotype in two genetic lines of the whitefly host, each with Rickettsia-infected and uninfected sublines. Introgression between the Rickettsia-infected subline of one genetic line and the Rickettsia-uninfected subline of the other was used to create two new sublines, each with the maternally-inherited extranuclear genetic lineages of one line (...