Hosts and pathogens are in a constant evolutionary arms race as hosts evolve to be better at resisting pathogens, and pathogens evolve to be better at infecting hosts. Our research focuses on studying this process from the hosts' perspective. Specifically, we try to understand if this interaction is resulting in signatures of selection at the same genes in divergent species. We recently found that in birds (and mammals!), genes under positive selection are likely to be immune genes, especially those that interact with viruses. Now, we are using data from bird populations to understand whether we observe these same genes under selection at more recent time scales. We are also investigating the process of pathogen-mediated selection by studying a time-series of House Finch genomes. House Finches were exposed to a new pathogen (Mycoplasma gallisepticum) in 1994, resulting in a 60% decline in many places. By studying how the genome has changed through time (before the new pathogen, 10 years after, and 20 years after) we are learning that resistance likely evolved at many regions of the genome rather than at a single gene. 

Plumage coloration is an ideal system for studying how natural and sexual selection shape trait evolution. To date, much of our research has focused on the evolution of tanager plumage coloration from the avian visual perspective, by comparing how plumage evolution evolves differently in males and females, how light environment has shaped the evolution of plumage coloration, and how competition has affected trait diversification. We are continuing work on the evolution of plumage coloration with an expansion in two directions. The first is to explore to study how the underlying coloration mechanisms (pigments, feather nano- and microstructure) evolve to produce the observed plumage coloration. Eventually we would like to better understand the genes that produce these coloration mechanisms evolve. The second is to understand how the many functions of feathers interact to shape different aspects of feather morphology.

One of the results of globalization has been the introduction of species from one part of the world to another. These introduced species are sometimes innocuous, mixing into the native ecological communities without much impact. However, they can also have huge impacts on native species, for example by competing for limited resources (e.g. nest cavities, food), bringing new diseases, or becoming new predators. Much research focuses on the impacts of introduced species to the native species, but the introduced species themselves can provide opportunities to understand the genomic impacts of a founder event (when a new population is established by a few individuals followed by an expansion) and how a species can adapt to a new environment - both important questions for conservation. We have used the House Finch as a model system to study the genomic impacts of introductions to the eastern United States and Hawaiian Islands. Moving forward, we will study the many introduced birds of Los Angeles (like the Pin-tailed Whydah, pictured to the left) to understand both how introduced species evolve in new environments as well as some of the impacts they have had on native species.