AWolbachia-associated fitness benefit depends on genetic background inDrosophila simulans

Abstract

The α-proteobacteriaWolbachiainfect a number of insect species and influence host reproduction to favour the spread of infected females through a population. The fitness effect of this infection is important in understanding the spread and maintenance ofWolbachiawithin and among host populations. However, a full elucidation of fitness effect requires careful control of host genetic background. Here, I transferred a single clone ofWolbachia(thewHa strain) into three genetically distinct isofemale lines of the flyDrosophila simulansusing microinjection methodology. These lines carried one of the three described mitochondrial haplogroups (siI,siII orsiIII) and differ in nuclear genome as well. Population cage assays showed thatwHa-infectedsiIII flies enjoyed a dramatic fitness benefit compared to uninfectedsiIII. In contrast,wHa did not affect the fitness ofsiI orsiII flies. This study points to the importance of host-by-symbiont interaction terms that may play an important role in organismal-fitness.