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

Abstract

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. We found that selection on both immune function and wing-spot size was significantly positive, and that selection on either trait was independent of selection on the other. We found no evidence of nonlinear quadratic or correlational selection. In contrast to previous studies, we found no phenotypic correlation between immune function and wingspot size. There was also no difference in immune response between territorial and non-territorial males. Our study suggests that predation may be an important agent of selection on the immune systems of prey, and because the selection we detected was directional, has the potential to cause phenotypic change in populations.

Wing Shape and Its Influence on the Outcome of Territorial Contests in the DamselflyCalopteryx virgo

“…For example, potential biases might result from variation in the relative proportions of fore- and hindwings that could be retrieved. This may explain the discrepancy with the study of Rantala et al (2011), where no evidence for selection on wing size could be found when relating predation risk to hindwing length.…”

“…While there seems to be little or no evidence that wing morphology plays a role in RHP, it has previously been shown that several wing characteristics affect predation probabilities (Svensson and Friberg 2007; Rantala et al 2011). Specifically for C. virgo , stabilizing selection has been detected on both wing width and wing length such that males with intermediate values for both traits had a better chance of surviving predatory attacks by white wagtails ( Motacilla alba ) (Svensson and Friberg 2007).…”

Evolutionary Ecology of Odonata: A Complex Life Cycle Perspective

“…One study reported that under a manipulated high predation risk, damselflies increased their mass less during the maturation period (96). Studies showed that consumptive predation may shift phenotypic distributions of several traits, including immune traits (76) and sexually selected traits such as body size and wing spot size (105). This indicates that both nonconsumptive and consumptive predation changes the adult phenotype and therefore is expected to indirectly shape fitness components such as life span, mating success, and fecundity.…”

Genomic features of the damselfly Calopteryx splendens representing a sister clade to most insect orders

“…The ability to defend and recover quickly from infections is clearly vital for survival and reproductive success, and previous studies have indicated that the melanization response is particularly important in this context (Rantala et al. 2010; Rantala et al. 2011; Kaunisto et al.…”