Principal Investigator: Briscoe, Adrianna D. Co-Principal Investigator: Reed, Robert D.
NSF Project Number: 1025106
Mimicry, the phenomenon by which organisms come to resemble distantly related distasteful or poisonous organisms, provides some of the strongest examples of adaptive evolution in the wild. While there is much evidence to suggest that the visual systems and color signals of aquatic animals evolve in tandem, the extent to which such correlated evolution exists in terrestrial animals like mimetic butterflies and their visual predators is largely an open question. This proposal is based on a recent discovery that duplication and positive selection of an ultraviolet-sensitive visual pigment in Heliconius butterflies coincided with the evolution of UV-yellow pigments on their wings which may serve as a signal to both visual predators and/or potential mates. The project seeks to investigate the evolution of wing pigments and visual eye pigments in Heliconius, and a community of cloud forest butterflies that mimic Heliconius using anatomical, molecular, physiological and computational modeling experiments. Together with environmental light measurements, these data will be used to refine computational models of butterfly and avian color vision to further our understanding of the potential benefit to the organisms of evolving new visual photoreceptors and signals in the ultraviolet range. A postdoc, graduate student and several undergraduates including members of underrepresented groups in the sciences will be trained in molecular biology, genetics, biochemistry and spectrometric methods. Genetic data will be deposited in the publically available database GenBank <www.ncbi.nlm.nih.gov/genbank/> and wing reflectance spectra will be made available online in journal and lab websites.
Mimicry, the phenomenon by which organisms come to resemble distantly related distasteful or poisonous organisms, provides some of the strongest examples of adaptive evolution in the wild. While there is much evidence to suggest that the visual systems and color signals of aquatic animals evolve in tandem, the extent to which such correlated evolution exists in terrestrial animals like mimetic butterflies and their visual predators is largely an open question. This proposal investigated the hypothesis that duplication and positive selection of an ultraviolet-sensitive visual pigment in Heliconius butterflies, which coincided with the evolution of UV-yellow pigments on their wings, served as a signal to both visual predators and/or potential mates. Scientific Merit: Using anatomical, molecular, physiological and computational modeling of avian and butterfly color vision, birds and butterflies with only one ultraviolet visual pigment in their eyes were shown to more easily confuse the UV-yellow wing pigments of Heliconius butterflies with the yellow wing pigments of non-Heliconius mimics. By contrast, Heliconius butterflies themselves whose eyes contain the duplicated UV opsin photoreceptors were more easily able to discriminate these color signals, thereby potentially more easily identifying potential mates in a community of non-Heliconius mimics. This is the first evidence that the evolution of a new animal color can simultaneously maintain a protective benefit against potential predators while serving as a salient signal to potential mates. Broader Impacts: Graduate students, including from an underrepresented group in the sciences, were trained in spectroscopy, molecular biology, and next-generation sequencing methods. Images generated from this project comparing the UV-yellow with yellow wing color patterns of Heliconius and co-mimics were broadcast on television in episode 5 of David Attenborough's Natural Curiosities television series.
