title: Protection of Pea Aphids Associated with Coinfecting Bacterial Symbionts Persists During Superparasitism by a Braconid Wasp.
abstract: Bacterial endosymbionts that associate facultatively with insect herbivores can influence insect fitness and trophic interactions. The pea aphid, Acyrthosiphon pisum, can be protected from parasitism by the braconid wasp Aphidius ervi when harbouring particular symbiotic bacteria, with specific endosymbiont coinfections providing almost complete protection. However, studies often quantify aphid mummification with no control over parasitoid oviposition per aphid; thus, if mummy production fails or is low, the causes are often unclear. Here, we show that the high level of protection associated with the coinfecting endosymbionts Hamiltonella defensa and X-type is maintained even when pea aphids are superparasitised. This contrasts strongly with the protection provided by H. defensa alone, which has been shown by others to be overcome by superparasitism. By dissecting aphids exposed to two parasitoid attacks, we reveal that A. ervi deposits eggs equally freely in endosymbiont-infected and uninfected nymphs, and lack of mummification in endosymbiont-protected nymphs arises from failure of the wasp eggs to hatch or emerging larvae to develop.
authors.affiliation: The James Hutton Institute, Dundee, DD2 5DA, UK.
authors.forename: K J
authors.initials: KJ
authors.lastname: Donald
authors.affiliation: The James Hutton Institute, Dundee, DD2 5DA, UK.
authors.forename: H V
authors.initials: HV
authors.lastname: Clarke
authors.affiliation: The James Hutton Institute, Dundee, DD2 5DA, UK.
authors.forename: C
authors.initials: C
authors.lastname: Mitchell
authors.affiliation: The James Hutton Institute, Dundee, DD2 5DA, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Cornwell
authors.affiliation: School of the Environment, University of Dundee, Dundee, DD1 4HN, UK.
authors.forename: S F
authors.initials: SF
authors.lastname: Hubbard
authors.affiliation: The James Hutton Institute, Dundee, DD2 5DA, UK. Alison.Karley@hutton.ac.uk.
authors.forename: A J
authors.initials: AJ
authors.lastname: Karley
mesh_terms: D000818:Animals; D001042:Aphids / Q000254:growth & development / Q000382:microbiology* / Q000469:parasitology* / Q000502:physiology; D004755:Enterobacteriaceae / Q000502:physiology*; D005260:Female; D007814:Larva / Q000254:growth & development; D008297:Male; D009758:Nymph / Q000187:drug effects; D013559:Symbiosis; D014863:Wasps / Q000502:physiology*
keywords: Acyrthosiphon pisum; Aphidius ervi; Facultative endosymbiont; Oviposition; Parasitoid; Wasp larva