Document Type



Doctor of Philosophy


Biology, Evolution

Date of Defense


Graduate Advisor

Patricia Parker, PhD


Dr. Jason Knouft

Dr. Bette Loiselle

Dr. Robert Ricklefs


The red-footed booby (Sula sula) is considered one of the most polymorphic seabirds, with three recognized major adult plumage types: (1) white; (2) white-tailed brown; and (3) brown, and several degrees of intermediates. The ratio of these color morphs varies among populations, with the white morph typically predominating. However, there are a few populations that present an inversed ratio of color morphs, such as Isla Europa in the Indian Ocean and the Galapagos archipelago, with the white-tailed brown or brown morphs predominating. I studied natural populations of red-footed boobies from three geographic locations, namely, the Galapagos archipelago, Johnston Atoll in the Pacific Ocean, and the Fernando de Noronha archipelago in the South Atlantic Ocean, to investigate the genetic basis of plumage polymorphism as well as possible mechanisms maintaining the polymorphism and variation in the ratios of color morphs. To determine the genetic basis of the polymorphism, I investigated the role played by the candidate locus Melanocortin-1 receptor (MC1R). By examining alleles in the MC1R locus in the context of phylogeny of the Sulidae family, I investigate the scope of involvement of the MC1R locus in determining the different plumage colors and patterns among the ten species in this family. Several potential mechanisms maintaining the polymorphism and the differential ratio of color morphs among locations were evaluated; both selective and neutral mechanisms were explored, such as non-random mating and limited gene flow, as well as historical evolutionary events such as founder effect and bottleneck events.

Included in

Biology Commons