The Dominance of Coinfecting Parasites' Indirect Genetic Effects on Host Traits.

AbstractIndirect genetic effects (IGEs) exist when there is heritable variation in one organism's ability to alter a second organism's traits. For example, parasites have antigens that can induce a host immune response, as well as disparate strategies to evade or suppress host immunity; among-parasite genetic variation in these antigens generates among-host variation in immune traits. Here, we experimentally show that the cestode parasite exerts an IGE on an immune trait (peritoneal fibrosis) in its threespine stickleback host: stickleback developed strong fibrosis after exposure to some parasite genotypes but not others.

The dominance of coinfecting parasites' indirect effects on host traits.

Indirect genetic effects (IGEs) exist when there is heritable variation in one species' ability to alter a second species' traits. For example, parasites can evolve disparate strategies to manipulate host immune response, whether by evading detection or suppressing immunity. A complication arises during coinfection, when two or more parasite genotypes may try to impose distinct IGEs on the same host trait: which parasite's IGE will be dominant? Here, we apply the notion of dominance to IGEs during coinfection.