Meeting Abstract
Non-essential, facultative, symbiotic microbes can provide their hosts with protection from parasites, pathogens, and predators. Recent work has found that two facultative secondary symbionts Serratia symbiotica and Hamiltonella defensa, provide their host, the phloem-feeding insect the pea aphid (Acyrthesiphon pisum), with protection against predation from the lady beetle Hippodamia convergens. By reducing the fitness of the aphid predator, aphid secondary symbionts indirectly defend their host against predation, since aphids reproduce clonally and are often found in large genetically identical groups. We have recently extended this work to look at the fitness effects of aphid secondary symbionts (Serratia symbiotica, Hamiltonella defensa, and Regiella insecticola) in another aphid predator, the invasive lady beetle Harmonia axyridis. Similar to previous results, we found the survival of juvenile lady beetles to be significantly reduced for those that were fed aphids with secondary symbionts Serratia, as well as Regiella, however no fitness costs were found for those fed aphids with Hamiltonella or no symbionts. The presence of aphid symbionts in the larval diet of Ha. axyridis was also found to significantly affect development time to adulthood. Interestingly, the survival effects appear to be different between the species of predator. Additionally, for both predator species, different symbionts had different affects suggesting that each symbiont reduces the survival of the predator through a different mechanism. This work provides yet another example of the often far-reaching and unexpected effects that endosymbionts can have in ecological systems and highlights the importance of expanding our study of endosymbionts to include the many ecological interactions of their host species.
