UC Berkeley

Since the advent of animal-mediated pollination, pollinators have evolved adaptations to optimize their intake of floral rewards (1). The hummingbirds are one such group of pollinators that have diversified into over 300 extant species (2). A hallmark of hummingbirds is their extraordinarily long bills that also vary dramatically in curvature. The intertwined relationship between variation in hummingbird bills and the corresponding variation in flower shapes, colors, and sizes they feed from have resulted in a suite of morphological, physiological, and behavioral adaptations that we are just beginning to understand. In this dissertation, I gathered morphological and genomic data to address the hypothesis that rapid adaptation in response to environmental change continues to shape natural variation in foraging traits of wild hummingbirds of North America. In Chapter 1, I found that a growing human population size and the introduction of supplemental feeders and Eucalyptus into California during the 20th century is consistent with rapid shifts in population size of the Anna’s Hummingbird, and has facilitated changes in bill size and shape associated with climate and resource density. In Chapter 2, I provide evidence that a novel form of ultraviolet vision occurs through pre-existing color vision mechanisms following a genomic deletion of the UV opsin in the Broad-tailed Hummingbird. Chapter 3 reveals that variation in floral preferences, bill morphology, and long-distance migration phenologies are linked in a population of the Broad-tailed hummingbirds at the phenotypic and genomic levels, and may provide a mechanism for subtle niche divergence and specialization between individuals in canonical foraging traits.