Collaborative Research: Phylogenetics of autoresistance in poison frogs as revealed by phylogenomics, neurophysiology, and comparative ecology

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Animals have evolved a variety of chemicals defenses against predators. A premier example is the toxic chemicals in the skin of poison frogs. Because these frogs are brightly colored, predators such as birds and snakes learn to avoid them. These toxins are alkaloids, found in many animals and plants. The frogs acquire these chemical defenses by eating ants and other arthropods that contain the alkaloids. These frog alkaloids (e.g., tetrodotoxin, batrachotoxin) are pharmacologically important and cause muscle paralysis, and disrupt breathing and cardiac function. At the cellular level, alkaloids affect ion channels, which control the transmission of nerve impulses. Surprisingly, the ion channels of poison frogs are are not affected by their own toxins; thus, deciphering how this evolved has important broader impacts that translate to human health. This research will use evolutionary trees to guide the activities: fieldwork to acquire and characterize natural alkaloids and collect ecological data on the species, molecular evolution of ion channel resistance to alkaloids, and neurophysiological effects of alkaloids on ion channels. The research will provide opportunities for students from the University of Texas and Indiana State University to jointly participate in international fieldwork, acquire new skills in bioinformatics, molecular modeling, genomics, and neurophysiology, as well as promote interactions between the two universities.The project will use Next-Generation DNA sequencing of transcriptomes, targeted sequencing of hundreds of genes, and bioinformatics methods to reconstruct evolutionary trees that will guide the research program with an experimental framework for explaining the origin of resistance, which has evolved multiple times in the poison frogs (family Dendrobatidae). Sequencing will also be used to identify novel amino acid replacements that may confer resistance to alkaloids. Computational modeling and in vitro assays of mutated ion channels will determine if these novel replacements provide resistance to natural and synthesized alkaloids. Fieldwork will focus on acquiring genetic samples, skin alkaloids, and color photographs from multiple populations of frogs, using natural history collection standards data collection and voucher specimens preparation. The combination of approaches will provide novel insights in the systematics of Dendrobatidae poison frogs, and also the evolution of auto-resistance to toxic alkaloids within the group.