Meeting Abstract
Natural selection is driven by the environment, yet how different environments alter relationships between traits and fitness (i.e. adaptive landscapes) is rarely quantified. For instance, despite the importance of size-structured intraguild predation (IGP) interactions to population dynamics, their role in shaping adaptive landscapes is unknown. Greater size structure may elevate mortality via increased predation, promoting greater variance in fitness of the IG prey (i.e. differences in landscape elevational change). Shifts in size structure may also alter the relative importance of traits associated with escaping predation versus improved competitive ability (i.e. changes in adaptive peak location). Here, we assessed selection on 480 uniquely marked dragonfly larvae (Pachydiplax longipennis; IG prey) in experimental pools where we altered the size structure of the IGP community by manipulating the presence of an IG predator (Anax junius) and the degree of size variance within the IG prey (high/low). Variance in fitness was greater in pools with the IG predator. Directional selection favored larger head sizes and lower body condition but did not vary in strength or direction among environments. However, correlational selection varied between IG predator environments. In pools without IG predators, selection favored large larvae with moderate body condition and intermediately sized larvae with high body condition. In pools with IG predators, selection only favored large larvae with relatively low body condition. Overall, these results indicate that variation in the size structure of the IGP community, via the presence of a top IG predator, primarily altered the elevational change and the location of the adaptive peaks on the adaptive landscape.
