Document Type



Doctor of Philosophy



Date of Defense


Graduate Advisor

Patricia Parker, Ph.D.


Robert E. Ricklefs

Elizabeth A. Kellogg

Robert C. Fleischer


The Galápagos flycatcher (Myiarchus magnirostris) is an endemic species to the Galápagos Islands, Ecuador, and is among the least studied Galápagos terrestrial birds. In this work I unveiled the origin and colonization history of the Galápagos flycatcher, and also the origin of the parasites that are currently found in/on this bird species. To determine the origin of the Galápagos flycatcher, I rebuilt the phylogeny of the Myiarchus genus using cytb and ND2, and applied a Bayesian approach to estimate its colonization time. I discovered that the closest living relative of the Galápagos flycatcher is Myiarchus tyrannulus (Brown-crested flycatcher) from Central and North America, and these two sister groups diverged approximately 850,000 years ago. To better understand the Galápagos flycatcher evolution in the Galápagos Archipelago, I used seven microsatellites and morphological characters to compare populations from seven islands. Correlation between genetic diversity and island size pointed to drift as an important diversification force. In general, morphological distances across islands were not correlated with pairwise genetic distances, and local adaptation through natural selection may possibly have contributed to that, but drift and phenotypic plasticity could not be excluded as explanations. To investigate the origin of the Galápagos flycatcher parasites I studied blood parasites, lice, and mites from Galápagos flycatchers (n = 254) and from M. tyrannulus (n = 74) in Costa Rica. We found that different parasite species from the Galápagos flycatchers have different origins: five parasite species colonized the Galápagos Islands with the Galápagos flycatchers’ ancestors (two louse species and three mite species), and two parasite species were acquired from the native bird community after the Galápagos flycatchers ancestors arrived to Galápagos (Haemoproteus blood parasite and Brueelia louse). To investigate why some parasites found on M. tyrannulus (Plasmodium blood parasite and Philopterus louse) did not colonize Galápagos, I looked at immune responses of M. tyrannulus from Costa Rica to their parasites. I found no evidence that these parasites are affecting the health of M. tyrannulus more negatively than the other parasites and in a manner that would hinder their ability to colonize Galápagos.

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