PREDATORS COME AND PREDATORS GO: THE REVERSIBILITY OF PREDATOR-INDUCED TRAITS

Abstract

While numerous studies have been conducted on the ecology and evolution of phenotypic plasticity, to really understand plasticity we need to expose organisms to different environments over several ontogenetic stages. In this way, we can examine whether organisms change their phenotypic strategy over ontogeny, whether there are developmental windows that constrain the development of plastic traits, and whether behavior is more reversible than morphology if the environment reverts back to its original state. I addressed these questions by examining predator-induced plasticity in gray treefrog tadpoles (Hyla versicolor). Using aquatic mesocosms, I reared tadpoles with a constant absence of predators, a constant presence of predators, and the addition or removal of predators at three different times during their larval period. Tadpoles changed their phenotypic strategy over ontogeny; early in ontogeny they responded to predators by hiding, reducing their activity, and developing relatively deep tail fins. Later in ontogeny the tadpoles no longer employed behavioral defenses but relied on a combination of greater mass, deeper tails, and shorter bodies. The phenotypic changes were inducible throughout most of ontogeny, suggesting that there were few developmental windows. Activity, tail depth, and body depth were highly reversible early in ontogeny but less reversible later in ontogeny; because hiding was only used early in ontogeny, I could not assess its reversibility. This reversibility should affect not only the induced species, but will likely transmit the effects throughout the larger ecological community.