Changes in the behavior of <i>Myzus persicae</i> (Hemiptera: Aphididae) in response to predators after transinfection with <i>Rickettsiella</i> (Legionellales: Coxiellaceae) endosymbionts

Infection with endosymbionts can cause changes in the phenotype of their insect hosts, particularly for life-history traits such as fecundity and temperature sensitivity. Economically important pests such as aphids carry different species of endosymbiotic bacteria, some of which have potential as biocontrol agents. The impact of newly transinfected bacteria on behavioral responses of aphids (Hemiptera: Aphididae) has rarely been explored; however, traits such as microhabitat selection and response to predators could disrupt or reinforce the effectiveness of biocontrol. In this study we compared the behavior of green peach aphids, <i>Myzus persicae</i> (Sulzer, Hemiptera: Aphididae), with or without a transinfection of the facultative endosymbiont <i>Candidatus Rickettsiella viridis</i> (Legionellales: Coxiellaceae). In whole plants assays, we tested differences in microhabitat selection, leaf surface productivity and response to the predatory ladybird <i>Hippodamia variegata</i> (Goeze, Coleoptera: Coccinellidae). The transinfection affected the variance but not the mean of leaf surface preference, with the infected line aphids being more consistent across days. Aphid productivity did not differ between surfaces nor was it affected by the infection. Choice tests suggested that ladybird preference was not affected by <i>Rickettsiella.</i> However, the aphid lines responded differently to the predator in that the infected aphids were relatively more common on the adaxial surface in the presence of the predator whereas uninfected aphids showed no difference. Our results suggest that transinfected <i>Rickettsiella</i> endosymbionts can change their hosts' behavior in subtle ways but their immediate impacts on the effectiveness of predator-based biocontrol are not necessarily clear.