DISSERTATION RESEARCH: The Evolution of Hummingbird Coloration and Courtship Displays

Arizona State University, Scottsdale AZ

Investigators

Abstract

Non-technical paragraph Animals possess an incredible diversity of exaggerated traits that they use for communication, and often animals communicate using multiple traits. How this signal diversity came about and why animals use more than one trait to communicate has long interested scientists. To understand why and how this diversity in multiple signaling traits evolved, we are studying hummingbird iridescent plumage and exaggerated courtship displays. Iridescent coloration is angle-dependent and hummingbirds can easily manipulate the color observed as they behaviorally display. The PIs are exploring how the surface and internal structures of iridescent feathers co-evolved with courtship displays (shuttles) across hummingbird species. The PIs work combines measurements of micro- and nano-scale structural morphology with behavioral ecology and evolutionary theory, allowing the PIs to understand hummingbird communication from the behavior down to feather architecture. Additionally, the PIs will collect data on hummingbird mating and courtship biology, especially in terms of how hummingbirds use their environment while courting, which could prove useful to future conservation efforts. Additionally, recent work on the structure of iridescent butterfly wing scales has helped the development of more efficient solar panels. The PIs work on the angle-dependent nanostructures of hummingbird feathers could further help improve solar panel efficiency through a better understanding of how biological materials directionally reflect specific wavelengths of light. Technical paragraph Animals exhibit a great diversity of ornamental traits and display behaviors, and many animals possess multiple such traits that they use to communicate. Previous work has explained the diversity in these traits by examining how they evolved in relation to the environment; however these traits can also interact with each other as they are displayed, which will further shape their evolutionary history. The PIs are testing how interactions between ornamental traits, display behaviors, and environment influence the diversity of these traits through a comparative study on several species in the bee hummingbird tribe. Bee hummingbirds are ideal for this type of study because they possess two types of conspicuous visual traits - iridescent plumage coloration and stereotyped courtship displays (shuttles) - that vary across species. Iridescent coloration is angle-dependent, such that the observed color changes depending upon the feather structure and viewing/lighting angles. Thus, perceived coloration is the result of interactions between behavioral displays, the environment, and the micro- and nanostructures of iridescent feathers. The PIs are currently studying the complex interactions between these factors in several hummingbird species to understand how each species produces a specific color that is perceived by a receiver, and how this varies interspecifically. The PIs are expanding this work by evaluating how variation in iridescent micro- and nanostructure of feathers helped shaped the evolutionary relationships between bee hummingbird plumage, display, and environment. This work allows the PIs to study how hummingbird communication evolved at multiple levels, from behaviors to nanostructure of their ornaments.