Genetic variation in the effect of a facultative symbiont on host-plant use by pea aphids
- 650 Downloads
Ecological specialisation on different host plants occurs frequently among phytophagous insects and is normally assumed to have a genetic basis. However, insects often carry microbial symbionts, which may play a role in the evolution of specialisation. The bacterium Regiella insecticola is a facultative symbiont of pea aphids (Acyrthosiphon pisum) where it is found most frequently in aphid clones feeding on Trifolium giving rise to the hypothesis that it may improve aphid performance on this plant. A study in which R. insecticola was eliminated from a single naturally infected aphid clone supported the hypothesis, but a second involving two aphid clones did not find the same effect. We created a series of new pea aphid–R. insecticola associations by injecting different strains of bacteria into five aphid clones uninfected by symbionts. For all aphid clones, the bacteria decreased the rate at which aphids accepted Vicia faba as a food plant and reduced performance on this plant. Their effect on aphids given Trifolium pratense was more complex: R. insecticola negatively affected acceptance by all aphid clones, had no effect on the performance of four aphid clones, but increased performance of a fifth, thus demonstrating genetic variation in the effect of R. insecticola on pea aphid host use. We discuss how these results may explain the distribution and frequency of this symbiont across different aphid populations.
KeywordsAcyrthosiphon pisum Host-plant specialisation Regiella insecticola Secondary symbiont Trifolium pratense
C. L. S. was supported by a NERC studentship. Our work complied with UK law.
- Mopper S, Strauss SY (1998) Genetic structure and local adaptation in natural insect populations: effects of ecology, life history, and behavior. Chapman and Hall, New YorkGoogle Scholar
- Müller FP (1962) Biotypen und Unterarten der “Erbsenlaus” Acyrthosiphon pisum (Harris). Z Pflanzenkd Pflanzensch—J Plant Dis Prot 69:129–136Google Scholar
- Russell JA, Moran NA (2006) Costs and benefits of symbiont infection in aphids: variation among symbionts and across temperatures. Proc R Soc B Biol Sci 273:603–610Google Scholar
- Sandström J (1996) Temporal changes in host adaptation in the pea aphid, Acyrthosiphon pisum. Ecol Entomol 21:56–62Google Scholar