Poison frog warning signals: From the rainforest to the genome and back again

Abstract

Signal communication is pervasive in nature and is used to convey information to both conspecifics and heterospecifics. Aposematic species use warning signals (e.g. bright coloration) to alert predators to the presence of a secondary defense (e.g., spines, toxins, etc). The presence of a conspicuous signal in combination with a secondary defense is thought to increase the efficiency of learned avoidance by predators and may prevent attacks altogether. Aposematism is widespread both geographically and taxonomically, and aposematic species are seen across the tree of life (including nudibranchs, invertebrates, and vertebrates). There are three main requirements for aposematism to function effectively. First, aposematic species must be able to produce a pattern that contrasts the environmental background (typically via chromatophores and pigments). Second, predators must be able to receive and learn to avoid preying upon aposematic individuals based on the signal. And finally, aposematism must confer a fitness benefit to the population of an aposematic species. In this dissertation I examine both the information that aposematic species convey and how the aposematic signal itself is produced. First, I examine whether the aposematic signal conveys detailed information to visual predators regarding an individual's specific level of toxicity--a key, but contentious, hypothesis of aposematic theory. Second, I test whether the aposematic signal is multimodal in vertebrates by determining whether they present non-visual predators with an olfactory cue/signal that contains sufficient information to indicate the possession of toxins and thus decrease the likelihood of attack. Additionally, I use gene expression data across multiple color morphs of an aposematic frog species to look at candidate color genes and how they influence coloration. Finally, I examine gene expression during developmental time periods that correlate with color deposition to examine how candidate color genes influence color production over developmental time and across multiple color morphs.