The effects of heat stress and symbiosis on pea aphid (Acyrthosiphon pisum) reproduction and survival across life stages Open Access

Tran, Emily (Spring 2018)

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Acyrthosiphon pisum, the pea aphid, is a tractable insect model system to study cost trade-offs between alternative forms of defense, particularly with the establishment and maintenance of a beneficial, symbiotic relationship with protective microbes. Although there has been research on behavioral and physiological defenses, more understanding is needed in how these defenses trade off with each other as well as how the maintenance of microbial symbionts impact biologically important traits like lifespan and fecundity. These costs can be exacerbated under stress, and heat shock is a common and relevant experimental stressor as climate change is expected to impact many ecological systems.

 A previous study observed this defense trade-off phenomenon between the winged polyphenism and symbiotic relationships in adult pea aphid populations when adults were exposed to a heat shock. Here, the aim of our research is to expand on that work and determine whether the age at which aphids are exposed to stress impacts this trade-off.

Two experiments were conducted. Experiment 1 focused on the effects of heat shock in aphids possessing primary symbiont Buchnera aphidicola with an alternative strain (CO21) of the symbiont Regiella insecticola across 2nd instar, 4th instar, and adult life stages. Experiment 2 expanded on this and utilized genetically identical aphid lines (clone LSR1) with Ui and CO21 strains of Regiella. Our results suggest that heat stress at younger life stages in a pea aphid may neutralize negative fitness consequences and possibly improve fitness by adulthood. In addition, there may be an interaction between heat stress and certain symbionts, but it is unclear how exactly they impact host fitness.

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