Matthew Shawkey, Univ. Akron, EAR-1251895 Julia Clarke, Univ. Texas, Austin, EAR-1251922
This award is being co-funded by NSF's International Science and Engineering section.
ABSTRACT The proposed research will greatly improve our knowledge of the physiology of melanin-based color production, will provide unique insight into the significance of color and color-based novelties to the evolution of birds, and may provide inspiration for new optical nanostructures. The recent discovery that evidence of feather coloration can be found in the fossil record in the form of preserved melanosomes (melanin-containing organelles) now allows investigation of plumage coloration in a framework considering both extinct and living dinosaur species. PIs propose to identify how melanosome morphology and chemistry relate to color production in extant birds, determine how these relationships may be altered by fossilization, and then use these data to test hypotheses on the significance of plumage color to avian evolution. This interdisciplinary proposal, involving morphology, paleontology, evolutionary biology and chemistry, is therefore divided into two linked sections with specific deliverables. In the first section, PIs will use ultraviolet-visible reflectance spectrometry to objectively measure color of extant feathers, scanning electron microscopy (SEM) to quantify melanosome morphology, synchrotron-based mass spectrometry to examine chemistry and atomic force microscopy to examine surface texture of melanosomes. The use of these multiple measurements, and statistical analyses to quantitatively identify relationships between them and color, will allow them to make confident reconstructions of color based on assessment of fossil samples. Experimental degradation of feathers and melanosomes will help PIs determine how melanosome shape and/or chemistry may be altered. The second section brings data from the first to address previously untestable hypotheses concerning the origin and role of color diversity in feather evolution. Using focused ion beam (FIB) milling and microscopy, PIs will identify the presence of novel morphologies contributing to color diversification in birds, i.e. iridescent nanostructures and hollow, flattened melanosomes that produce some of the brightest colors in nature. That will allow PIs to estimate how melanosome morphological diversity and thus color may have shifted from early in evolution of feathers through modern birds and whether this diversification was associated with major transitions in the evolution of feathers. The color of dinosaurs presents an engaging context to bring fundamentals of chemistry, physics, and biology to the classroom and the lay public. PIs propose several public outreach programs that will capitalize on strong public interest in this work. Development of publicly available data analysis tools will allow broad applications of their techniques by the scientific community.
