Predation selects for increased immune function in male damselflies, Calopteryx splendens.

Predation selects for numerous traits in many animal species, with sick or parasitized prey often being at high risk. When challenged by parasites and pathogens, prey with poor immune functions are thus likely to be at a selective disadvantage. We tested the hypothesis that predation by birds selects for increased immune function in a wild population of male damselflies Calopteryx splendens, while controlling for a trait known to be under selection by bird predation, dark wing-spots.

Immune system activation interacts with territory-holding potential and increases predation of the damselfly Calopteryx splendens by birds.

Activation of the immune system in insects has been shown to be costly in the laboratory setting, but experimental studies in the field are lacking. The costs of immunity in the wild may be different to those in the laboratory because animals in the wild are simultaneously subjected to a suite of selective agents. We have measured the costs of immune system activation in a wild population of the territorial damselfly Calopteryx splendens.

Activation of the immune system promotes insect dispersal in the wild.

Dispersal has important ecological and evolutionary consequences but is a poorly understood behaviour. We experimentally tested whether activation of the immune system affects dispersal in male damselflies, Calopteryx virgo, from three natural populations. We show that males that contained an experimentally inserted artificial pathogen, a nylon monofilament implant, had higher dispersal rates and flew further than control males, but not further than sham manipulated males.