"Defensive symbiosis - tales from an uneasy alliance"Smith, CameronDefensive symbiosis is a biological phenomenon which sees a symbiotic relationship between a host and a microbe provide additional protection to a host against something harmful. Defensive symbionts are therefore promising agents of biocontrol that could be used to control or ameliorate the impact of infectious diseases. Previous theory has shown how symbionts can evolve along the parasitism–mutualism continuum to confer greater or lesser protection to their hosts and in turn how hosts may coevolve with their symbionts to potentially form a mutualistic relationship. However, the consequences of introducing a defensive symbiont for parasite evolution and how the symbiont may coevolve with the parasite have received relatively little theoretical attention. Here, using a theoretical approach, we will see how different types or mechanisms of protection can affect the evolution of the harmful pathogen. We further determine the effects that the coevolution of the symbiont and pathogen can have on host outcomes. |
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