REDUCING PREDATION THROUGH CHEMICALLY MEDIATED CAMOUFLAGE: INDIRECT EFFECTS OF PLANT DEFENSES ON HERBIVORES

Abstract

Herbivores often specialize on particular hosts that provide both food and shelter from natural enemies. It is thus often unclear whether a plant’s value as a food or its value as a safe shelter has played a larger role in selecting for specialization. Decorator crabs offer a novel opportunity to investigate the relative effects of diet vs. natural enemies in selecting for specialization because these crabs place plant “shelter” on their backs as camouflage but need not use these plants as food, thus decoupling the plant’s value as a food from its value as a shelter. In this study, we show that juveniles of the decorator crab Libinia dubia selectively decorate with the chemically defended brown alga Dictyota menstrualis but treat this plant as a low-preference food. Common omnivorous fishes that are potential predators of Libinia avoid consuming Dictyota due to the alga’s potent chemical defenses. In the field, juvenile crabs decorated with Dictyota experience significantly less predation than crabs decor...