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ViewAttendees 7

SysEB

Student Competition 10-Minute Paper

Grad 10-min: SysEB, Symbionts

Nested complexity and trench-warfare dynamics: Field variation in a bacteriophage of an aphid endosymbiont

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Student Competition On-Demand
Acythrosiphon pisum, the pea aphid, engages in symbiotic relationships with multiple defensive facultative symbionts. These bacteria can confer resistance against a variety of threats, from pathogens to heat-stress. The presence or absence of these symbionts, combined with the strain-level variation in some symbiont species, allows for a complex system in which to study symbiosis. One of the most common symbiont species in pea aphids, Hamiltonella defensa, exhibits genome-level variability, in addition to variation in its harbored APSE bacteriophage, which allow H. defensa to provide anti-parasitoid defense to pea aphid hosts. The assumptions that the genotypes of both H. defensa and APSE are relevant to the anti-parasitoid defensive phenotype, and that parasitoids can evolve counter-resistance, lead to expectations of complex coevolutionary relationships. Across several years our lab has monitored pea aphid populations from multiple North American populations, examining the varieties of H. defensa and APSE and their variation over space and time. Though PCR screening and DNA sequence analysis, we here show substantial turnover at both levels, revealing that phage can be dynamic in otherwise closely related H. defensa within a single population over time. This pattern is reminiscent of the expectations of the trench-warfare model of coevolution described in host-pathogen literature, suggesting a need for future studies on to more precisely pinpoint the specificity of anti-parasitoid defense and counter-adaptation.