Morphological and behavioral defenses in dragonfly larvae: trait compensation and cospecialization

Many animals have two basic traits for avoiding being killed by a predator: behavioral modification and morphological defense. We examined the relationship between antipredator behavior and morphological defense in larvae of three closely related dragonfly species within the genus Leucorrhinia. The three species differ with regard to their morphological defense as expressed in the length of the larval abdominal spines. Results showed that longer abdominal spines provided protection against an attacking fish predator (perch) because the probability of being rejected after an attack was significantly higher in the species with the longest abdominal spines. In contrast to other studies, the species with the strongest morphological defense did not show the least behavioral predator avoidance. Instead, the species with intermediate morphological defense showed the least predator behavioral avoidance. The results suggest that the Leucorrhinia system is a mixture of trait cospecialization (a positive correlation between antipredator behavior and morphological defense) and trait compensation (a negative correlation between antipredator behavior and morphological defense). Differences in the relationship between morphological and behavioral defense between species might be related to abundance patterns of the three species in lakes with and without fish predators.