The Evolving Opportunistic Pathogen Communities on Host Individuals and the Evolution of Host Aging

Abstract

Abstract In the coevolution of host and the associated opportunistically pathogenic microbiota, the microbiota has an advantage of a smaller generation time and thereby faster evolution. Sexual reproduction by the host is hypothesized to be the hosts- evolutionary counter-strategy. We propose further that the ticking clock of the evolving microbiota influences the evolution of host aging. Modeling these dynamics shows that if transmission of microbes has a small to moderate vertical or kin-biased component, early aging can evolve in the host. Host genotypes with shorter longevity are more likely to escape pathogen evolution thereby getting a selective advantage for their progeny when risk of infection is high. As parasite communities are ecologically and evolutionarily dynamic, hosts can in response evolve plasticity in aging. The model shows that a genotype which activates aging or death pathways in response to threshold parasite colonization gets a selective advantage whenever there is a nonzero kin transmission bias. The hypothesis is compatible with classical hypotheses for aging. We make many predictions testable by epidemiological, comparative or experimental methods.