DISSERTATION RESEARCH: The Relative Roles of Chemical and Visual Communication in Heliconius Butterflies

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A wide variety of animal species enjoy relative safety from predators due to chemical compounds that render them unpalatable. Such species often exhibit warning signals that predators learn to avoid. In many cases, non-toxic species have evolved to take advantage of this by mimicking the coloration, form, behavior, or odor of unpalatable ones to deceive predators. Alternatively, warning signals in different toxic species may converge, reducing the cost of training predators. Despite the large amount of theoretical and empirical work on the origins and stability of mimicry, very little is known about the conflicts that similarities between co-mimics (two or more species that mimic each other) might create for species recognition and communication within either species. Butterflies, show numerous instances of mimicry, and are a good model system to study such signaling conflicts. These insects generally find and recognize mates using visual cues, and differences in wing color patterns often prevent mating mistakes, keeping closely related species reproductively isolated. At the same time, such colorations may also be used as anti-predatory warning signals in toxic species. When coexisting mimetic species have converged in wing color patterns that are used as warning signals, a conflict between interspecific mimicry and intraspecific recognition is likely. In such cases, a shift towards alternative recognition cues in the form of olfactory signals or mating strategies that reduce the possibilities of recognition conflict is expected. The main goal of this project is to identify recognition mechanisms that reduce signal conflict, and their role in the evolution of mimicry between closely related species in Heliconius butterflies. To address these objectives, first the main compounds in female abdominal odors will be identified to test whether signals vary in the way predicted to reduce the conflict between species with similar colorations. Then, choice experiments and chemical analyses will used to determine the relative importance of chemical and visual signals in a unique mating system exhibited by some Heliconius species, where the butterflies locate potential mates at the pupal stage, thus reducing reliance on wing patterns for recognition. Broader impacts. The co-PI, who will be conducting the work, is a female Latin American graduate student. The research will involve training of undergraduates, in butterfly rearing and experimentation under greenhouse conditions. In the past, several undergraduates (the majority women) trained in the lab have made use of the Heliconius model system to conduct their own research to address original scientific questions. This work also promotes international cooperation between students and faculty at the University of Texas (USA) and the Institute of Organic Chemistry, TU Braunschweig (Germany). We anticipate at least three major publications derived from this research, and the participation of the co-PI and undergraduates in local and international scientific meetings. This project is funded by the Division of Integrative Organismal Biology and the Office of International Science and Engineering.