Ultimately, my interests surround question-based research in evolutionary ecology of vertebrates. My specialization is in the evolutionary ecology of immune genes (however, I am not restricted to this area of research). This may involve signals of adaptive genes, such as the major histocompatibility complex. I am currently researching chemical ecology, immunogenetics, behavior, and microbial symbionts in songbirds at the BEACON Center for the Study of Evolution in Action at Michigan State University.
You may ask yourself: “How does one study chemical ecology in songbirds? Don’t they just communicate through singing and plumage?”
While acoustic and visual cues are still important, chemical cues are coming into the forefront of communication in songbirds. Recent research, particularly from Dr. Danielle Whittaker, has shown that dark-eyed juncos (Junco hyemalis) respond to chemical cues from preen oil secreted by their uropygial gland. This candidate cue is involved in reproductive success in this species and may be mediated by microbial symbionts located in and around this gland. Alongside Dr. Whittaker, I am trying to unravel how host genotype controls the abundance and taxonomic groups of bacteria in the preen gland of this species.
How do you take preen oil from a bird you ask?
Other research endeavors involve investigating the role of immune genes on host-pathogen interactions, and how these interactions are involved in population divergence, and animal conservation.
Ph.D. (Supervisor: Beth MacDougall-Shackleton)
Thesis Abstract: In recent years, sexual selection theory has redefined genetic quality to consider not only additive genetic effects on fitness but also non-additive genetic effects, such as heterozygote advantage or disadvantage. In jawed vertebrates, the major histocompatibility complex (MHC) gene family has been shown to exhibit both additive and non-additive genetic effects on fitness. MHC gene products are involved in initiating adaptive immune responses, and MHC genotype determines the range of pathogens to which an individual can respond. Therefore, parasite-mediated selection at MHC may favour locally-adapted, rare, or particular combination of alleles. Because heterozygote advantage at MHC is widespread, sexual selection should favour mechanisms by which individuals assess the MHC genotypes of potential mates, and mate non-randomly. Studies exploring the role of MHC in immunity and sexual selection are widespread amongst mammals and fish, but in birds (especially songbirds) there is relatively scant evidence for MHC-mediated mating and the mechanism by which this might be accomplished remains unknown. First, I assessed differentiation at MHC class I and II that might underlie locally-good gene effects in two populations of song sparrows (Melospiza melodia) previously shown to exhibit higher resistance to sympatric malaria (Plasmodium) strains. I found no population differentiation, suggesting no locally-good gene effects at MHC, but individuals with higher class I diversity were less likely to be infected when experimentally inoculated with Plasmodium. Second, I explored whether song sparrows convey information on MHC class II genotype through chemical (preen oil) or auditory (birdsong) cues. Pairwise similarity at MHC was related to pairwise similarity of preen oil chemical composition (Figure 1a: r=0.11, p=0.002), but not to pairwise similarity in song repertoire content. Song repertoire size, a sexually selected trait in this species, was nonlinearly related to MHC diversity, such that males with intermediate MHC diversity sang the most songs. Finally, to investigate MHC-mediated mate choice, I compared MHC similarity of socially mated pairs of free-living song sparrows to random expectations. Contrary to my prediction of MHC-disassortative mating, social pairs were more similar at MHC than expected by chance (Figure 1b: p=0.0176). This work emphasizes the importance of considering mate choice in the context of fitness effects at MHC.
Note: Figure 1a — This is still one of the coolest studies I have ever performed, however, the wild data has noise from both axes. Each data point represents a pairwise comparison between a male-female dyad. The data came from preen oil and MHC from gDNA in wild song sparrows. Although I found a significant trend, I feel captive studies would clean up this relationship since captive birds would have a standardized environment (food, light, hormones; which can all affect preen oil composition), and that characterizing MHC from cDNA would capture all true alleles, as gDNA may contain pseudogenes.
MSc (Supervisor: Colleen Barber)
Thesis Abstract: Plumage spectral characteristics are thought to play an essential role in mate choice. Male and female birds may benefit from mating outside of their social-pair bond if they obtain genetic benefits for their offspring by choosing mates with plumage that signals individual high quality. The goal of this thesis was to test the hypothesis that male and female genetic quality is signaled through hackle spectral characteristics and used in mate choice decisions by European starlings (Sturnus vulgaris). Hackle brightness was positively correlated with female body condition and male provisioning effort. Also males with brighter hackles sired proportionally more male offspring than males with duller hackles. Purple hackles (Figure 1a, Figure 2) were positively correlated with male body condition and female realized reproductive success. This study demonstrates the importance of hackle spectral quality in European starlings and the role it plays in mate choice.