Symbiotic relationships between insects and microorganisms are common in nature. For instance, pea aphids (Acyrthosiphon pisum) harbor not only the well-studied primary endosymbiotic bacterium Buchnera aphidicola, but also a suite of facultative secondary symbionts (SS). These SS are maintained in significant numbers in natural populations, indicating that SS may be providing a net fitness benefit to their aphid hosts. To explore the potential fitness benefits to aphids of harboring SS, I examined the possibility that two pea aphid SS (R and U-types) confer resistance to their primary natural enemy, the braconid parasitoid Aphidius ervi. Pea aphids vary genetically in resistance to parasitism by A. ervi so the tests were performed using cohorts of artificially infected and uninfected individuals of the same aphid clone. There is evidence that the R-type, but not the U-type SS, confer resistance to parasitoid attack by A. ervi. Further tests determined that the mechanism of resistance involves host suitability rather than host acceptability.
Species 1: Hymenoptera Braconidae Aphidius ervi
Species 2: Hemiptera Aphididae Acyrthosiphon pisum (pea aphid)
Keywords: symbionts, host fitness
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA