I earned my BS in Environmental Biology from California Polytechnic State University in Pomona in 2014. I'm earning my PhD at San Diego State University, studying genetics, behavior, and morphology in Allen's and Rufous Hummingbird. These two species hybridize in southern Oregon, and form the basis of most of my current work. In addition, I'm investigating the phylogeography of Allen's Hummingbird to decipher which populations are undergoing expansions versus declines.
Hybridization between Allen's and Rufous Hummingbird
Myself and collaborators are in the midst of revealing a new hybrid zone between two popular species of hummingbird using genetic, behavioral, and morphological data. The most unique part of our approach is in our use of behavioral data in diagnosing hybrid individuals. In both species, courtship involves a male performing an initial ascent and subsequent
J-shaped dive, with a couple of diagnostic differences present between the dives of each species. During the dive, a species-specific sound is
emitted by the tail feathers of the displaying male. In addition, Allen’s Hummingbird exhibits a novel
behavior occurring immediately before the dive, the pendulum display, where the
bird slowly flies back and forth in a shallow U-shape. Both displays can be
broken into distinct elements, and some elements of the dive are the same as those in the pendulum display. When a hybrid male displays to a female hummingbird, the behaviors he exhibits incorporate behavioral elements representative of each parent, often making identification simple during the breeding season.
How does selection act on this hybrid zone?
Through investigation of genetic, morphological, and behavioral data across the hybrid zone, I am assessing whether prezygotic (before mating isolation; for example, female choice occurring after a male performs a courtship display), postzygotic (after mating; hybrid incompatibility or inviability) isolation, or both are important drivers of isolation across the hybrid zone. Further, this chapter of my dissertation addresses several other questions- what role does the environment have in shaping the hybrid zone? Do hybrids outcompete their progenitors in certain parts of the hybrid zone? How are different characters distributed across the area of contact? If certain characters are only present on one side of the hybrid zone, they are likely important to the speciation process. This area of my research highlights an underlying theme in evolutionary biology- how can speciation occur, and what traits might drive this process?
Admixture mapping of hybrid phenotypes
Through admixture of phenotypes and
genotypes, naturally occurring hybrid zones provide ideal tools to study how
differentiation and novelty arise. In my dissertation, I am using this hybrid zone to
investigate the evolution of
behavioral novelty. Because Allen's and Rufous Hummingbird behaviors are stereotyped, innate, and under
genetic control, I am using this naturally occurring hybrid zone to determine the genes contributing to expression of the pendulum display in Allen's Hummingbird, and study how
the expression of the pendulum display in Allen's Hummingbird evolved.
Phylogeography of the Allen's Hummingbird
Because some populations appear to be declining, Allen’s Hummingbird is currently listed on the Partners in Flight Conservation Watchlist. Allen’s Hummingbird consists of two subspecies: Selasphorus sasin sasin and Selasphorus sasin sedentarius. S. s. sedentarius was previously endemic to the Channel Islands, but is now widespread throughout southern California. S. s. sasin is 15% smaller than S. s. sedentarius and is found from Oregon south to Santa Barbara County. No previous study has investigated the genetic distinctiveness of these two subspecies or the extent to which gene flow is occurring between the two subspecies. Using genetic data in conjunction with my phylogeographic study, as well as available genetic data from museums, my research will clarify which parts of the distribution are undergoing expansions versus declines, and evaluate the species placement on the Partners in Flight Watchlist.