APV infection does not alter symbiont-mediated protection against other mortality agents: We next examined whether the protective effects of R. insecticola against P. neophidis or H. defensa against A. ervi were also influenced by virus co-infection. Results strongly indicated the protective effects ofR. insecticola against P. neophidis were not reduced by APV infection as measured by much higher aphid survival and lower fungal sporulation when compared to aphids without R. insecticola (Fig 2A, B, Table S4). However, APV infection of aphids without R. insecticola, resulted in lower survival and higher fungal sporulation rates than infection with P. neophidis alone (Fig. 2A-C). The high-level protective effects of H. defensa /APSE-3 (ND18.H3) and moderate protective effects of H. defensa /APSE-2 (5D-AB.H2) against A. ervi were also not lowered by APV infection (Fig. 2D-I; Table S5). For aphid lines without facultative symbionts, aphid survival was very low, while successful wasp development (mummification) was high, but these did not generally differ between APV positive and negative lines (Fig. 2D-I; Fig S1; Table S5). The one exception to this latter trend was the WI246-8 line, which produced fewer mummies if infected with APV (W1246-8+APV) but this outcome was also associated with more aphids dying while also not producing a parasitoid (dual mortality) rather than an increase in aphid survival (Table S5; Fig. S1E, F).
Since parasitoid fitness is known to be influenced by host quality, we also examined whether A. ervi developing in hosts infected by APV exhibited reduced fitness by estimating the size of emerging female wasp offspring. We found that smaller female A. ervi were produced from APV-infected aphids in three of the four assayed aphid lines that lacked facultative symbionts (Table 4A, B). We did not measure the size of emerging wasps from aphids hosting H. defensa /APSE-3 because very few mummies were produced due to the high level of protection this strain confers. However, we did measure the size of female wasp offspring that developed in aphids hosting H. defensa /APSE-2. Interestingly, no differences were detected between the size of wasps that emerged from aphids with H. defensa/ APSE-2 that were persistently infected with APV versus aphids that were not virus infected (Table 4B).