Multiple phenotypes conferred by a single insect symbiont are independent.

Many microbial symbionts have multiple phenotypic consequences for their animal hosts. However, the ways in which different symbiont-mediated phenotypes combine to affect fitness are not well understood. We investigated whether there are correlations between different symbiont-mediated phenotypes. We used the symbiont , a striking example of a bacterial symbiont conferring diverse phenotypes on insect hosts. We took 11 strains of infecting pea aphids () and assessed their ability to provide protection against the fungal pathogen and the parasitoids and . We also assessed effects on male offspring production for five of the strains. All but one of the strains provided very strong protection against the parasitoid . As previously reported, variable protection against and was also present; male-killing was likewise a variable phenotype. We find no evidence of any correlation, positive or negative, between the different phenotypes, nor was there any evidence of an effect of symbiont phylogeny on protective phenotype. We conclude that multiple symbiont-mediated phenotypes can evolve independently from one another without trade-offs between them.