Origins of aposematism in poison frogs
Over the last 50 million years, poison frogs (family Dendrobatidae) have evolved to sequester alkaloids from diminutive arthropod prey three independent times. Along with origins of chemical defense, these dendrobatids have undergone extensive changes in metabolism, skin morphology, diet, coloration, behavior, and neurophysiology. Thus, poison frogs present an excellent system for identifying mechanisms underlying the origins and diversification of complex novel phenotypes.
Why don't poison frogs poison themselves? Their chemical defenses target a variety of ion channel proteins in nervous systems that govern action potentials and neurotransmitter release. Any organism susceptible to these chemicals would not survive being covered in them. We study evolutionary changes in nervous system proteins that are targeted by poison frog chemical defenses, such as voltage-gated sodium channels and nicotinic acetylcholine receptors.
Among the 300 species of dendrobatid poison frogs, the Epipedobates clade is the youngest group that is both chemically defended and brightly colored, offering a glimpse into incipient origins of aposematism. By studying the extensive phenotypic variation in Epipedobates, we are illuminating the evolutionary pathways, population dynamics, and molecular mechanisms underlying the complex ecological shift to aposematism.