Predation and the relative importance of larval colour polymorphisms and colour polyphenism in a damselfly

Intraspecific body colour variation is common in many animal species. Predation could be a key selective agent giving rise to variation in body colour, and such variation could be due to genetics (polymorphisms) or phenotypic plasticity (polyphenisms). In this study we examined the degree of colour polymorphism and polyphenism in background colour matching in larvae of the damselfly Coenagrion armatum. In addition, we tested if predation risk is reduced when larvae are exposed to a matching compared to a non-matching background. By raising families of larvae at three different background colours we showed that polymorphism explained about 20 % of the total variation and polyphenism about 35 %. In a predation experiment with fish, we showed that larvae with a body colour matching the background had a higher survival success compared to larvae with a non-matching background colour. We suggest that the background matching is adaptive in terms of survival from predation and that colour diversity is maintained because of spatial and temporal variation in the background experienced by damselfly larvae under field conditions.