The evolution of genetic bandwagoning

Abstract Background In separate literatures, biologists have marshaled theoretical and empirical support for theories that a variant can be selected to (1) induce suicide by moribund or otherwise stressed holders; (2) induce suicide by a holder with low productive or reproductive potential; (3) impose senescence upon a chronologically old holder; and (4) reduce the yield of a holder with low genetic heterozygosity. High stress, moribundity, low productive and reproductive potential, high chronological age, and low genetic heterozygosity all indicate the holder has a relative paucity of advantageous genetic variants in acquiring prey, territory, and mates or surviving predators and parasites. Therefore, an unappreciated commonality between these theories is that a variant can be selected that reduces the fitness of a holder of low genetic quality. Here, I argue that a variant can be selected that reduces its holder’s fitness in response to not just these indications but also other indications of low genetic quality. The fitness losses induced by the variant in low-quality individuals allow fitness gains for nearby individuals, some of which hold a copy of the variant. The variant gains frequency by hitchhiking along with (“jumping on the bandwagon” of) higher-quality individuals (and their lineages) that have copies of the variant; therefore, it is called a “bandwagoning” variant. Questions What parameter values (e.g., population quantity, relatedness, heritability of reproductive success) allow natural selection of genetic bandwagoning? Features of the model The model is an individual-based Moran process. Each individual’s quality value is randomly chosen at birth from a normal distribution that has a mean equal to the quality value of its parent. Ranges of parameters Total population quantity varied from 50 to 500. Assortment (“relatedness”) in the population varied from .05 to .15. Recorded values for the heritability of reproductive success varied from .024 to .132. Conclusions Natural selection of genetic bandwagoning can occur even when values for population quantity, relatedness, and heritability of reproductive success are low enough to be in line with reported values for humans and other species. Therefore, genetic bandwagoning theory can explain why indications of an organism’s low genetic quality induce behavior by, or biological processes within, that organism that reduce that organism’s fitness.