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Open Access Research article

Aphid facultative symbionts reduce survival of the predatory lady beetle Hippodamia convergens

Kelly Costopoulos1, Jennifer L Kovacs12*, Alexandra Kamins1 and Nicole M Gerardo1

Author Affiliations

1 Department of Biology, O. Wayne Rollins Research Center, Emory University, 1510 Clifton Road N.E, Atlanta, GA 30322, USA

2 Department of Biology, Spelman College, 350 Spelman Lane, S.W, Atlanta, GA 30314, USA

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BMC Ecology 2014, 14:5  doi:10.1186/1472-6785-14-5

Published: 20 February 2014

Abstract

Background

Non-essential facultative endosymbionts can provide their hosts with protection from parasites, pathogens, and predators. For example, two facultative bacterial symbionts of the pea aphid (Acyrthosiphon pisum), Serratia symbiotica and Hamiltonella defensa, protect their hosts from parasitism by two species of parasitoid wasp. Previous studies have not explored whether facultative symbionts also play a defensive role against predation in this system. We tested whether feeding on aphids harboring different facultative symbionts affected the fitness of an aphid predator, the lady beetle Hippodamia convergens.

Results

While these aphid faculative symbionts did not deter lady beetle feeding, they did decrease survival of lady beetle larvae. Lady beetle larvae fed a diet of aphids with facultative symbionts had significantly reduced survival from egg hatching to pupation and therefore had reduced survival to adult emergence. Additionally, lady beetle adults fed aphids with facultative symbionts were significantly heavier than those fed facultative symbiont-free aphids, though development time was not significantly different.

Conclusions

Aphids reproduce clonally and are often found in large groups. Thus, aphid symbionts, by reducing the fitness of the aphid predator H. convergens, may indirectly defend their hosts’ clonal descendants against predation. These findings highlight the often far-reaching effects that symbionts can have in ecological systems.

Keywords:
Symbiosis; Mutualism; Symbiont-conferred protection; Serratia symbiotica; Hamiltonella defensa; Pea aphid; Acyrthosiphon pisum; Predation; Defensive mutualism; Protective symbiosis