Doctor of Philosophy, University of Akron, 2014, Integrated Bioscience
A longstanding question in biology is why phenotypic diversity is unevenly distributed across the tree of life. Such differences can be caused by both extrinsic (e.g., natural selection) and intrinsic factors (e.g., how a trait functions). Despite numerous examples of diversification in form and function of complex biomechanical traits, we know relatively little about these processes in ornamental traits. Diverse ornamental feather colors in birds can be produced either by absorption (pigment-based colors) or scattering of light by feather nanostructures (structural colors). Because structural colors are deterministically related to the nanostructures that produce them, they are excellent systems to study form-function relationships and diversity of ornamental traits. In my dissertation I combine methods from physics and evolutionary biology to understand how proximate mechanisms explaining color (coherent light scattering) explain patterns of color diversity using iridescent feathers as a model system. Specifically, I ask two fundamental questions, one proximate and one ultimate, about iridescent colors: i) How are iridescent colors produced? and ii) What are the implications of how iridescent traits function for how they evolve? To tackle these questions, I sampled a nanostructurally diverse range of species, quantified their nanostructures with TEM and optical microscopy, experimentally tested the roles of different nanostructural traits in producing color by modifying them at the nanometer scale with FIB milling or humidity changes, and linked form and function with optical modeling. I then used simulation-based approaches and large-scale comparative analysis of color diversity to explore evolutionary consequences of functionally modular nanostructures in feathers. Together, my results suggest that morphological novelties in birds have, at least in part, allowed birds to achieve their vast morphological and colour diversity, and the way a color is produced has i (open full item for complete abstract)
Committee: Matthew Shawkey Dr. (Advisor); Blackledge Todd Dr. (Committee Member); Luettmer-Strathmann Jutta Dr. (Committee Member); Dhinojwala Ali Dr. (Committee Member); Doucet Stephanie Dr. (Committee Member)
Subjects: Biology; Physics