Uncovering symbiont-driven genetic diversity across North American pea aphids

The pea aphid, Acyrthosiphonpisum, harbors a diverse array of heritable bacterial symbionts with known roles in defense. Most studies on the diversity of symbionts within pea aphid populations have tended to use diagnostic surveys, targeting a limited range of the presently known (and potential) symbiotic associates. To provide a more thorough investigation of bacterial symbionts, we applied two methods using universal PCR primers—DGGE and 454 pyrosequencing of 16S rRNA genes—to study bacteria in aphids from five populations. Our findings reveal that up to seven symbionts can be found within single populations, that co-infections are quite common, and that numerous strains from at least three symbiont species are found within pea aphid populations. Combined, it is clear that this symbiotic diversity creates a large degree of heritable, and functionally important, variation within pea aphid populations.