The overarching goal of my current research is to understand the interface between social behavior, signaling traits, and physiology. This involves experimental approaches to studying social networks in a free-living facultatively social bird species (barn swallow, Hirundo rustica) using novel digital proximity loggers that record social interactions among individuals. In this system, a mate-selection signal, ventral plumage color, indicates individual quality and has been associated with stress and androgen hormone levels. In collaboration with Rebecca Safran, I am testing hypotheses about how phenotypic traits structure social networks and how social feedback affects aspects of physiology (stress response, androgen levels, oxidative stress, antioxidants, and gut microbial diversity). We are currently working with Dr. John Burt, who makes Encounternet digital transceiver tags for obtaining social contact data, and Dr. Bailey Fosdick, a network statistician. Our findings have been published in Biology Letters and PLoS ONE. The work was recently featured in the University of Colorado's alumni magazine, The Coloradan!
Current research projects include:
The integrated phenotype: social behavior, testosterone, and signaling traits
Social and parental care behavior in barn swallows
Early life effects on telomere length
Haemosporidian parasites in migratory and resident birds in Georgia
Photo on left: 2017 summer research students in the Levin lab. L-R: Jazz Stephens, Vaughn Wicker, Alina Ibrahim, Iris Levin
Haemosporidian parasites in Galapagos: The role of migrants
My postdoctoral research with Patty Parker, collaborators and three undergraduate students focused on Plasmodium in Galapagos. Since our discovery of a Plasmodium lineage in Galapagos penguins, we had found additional lineages in yellow warblers and Galapagos finches. These mentored undergraduate projects focused on testing samples from bobolinks breeding in Nebraska, Vermont and Oregon for haemosporidian parasites. The bobolink is the only passerine bird that regularly migrates through Galapagos on its way to overwinter in Argentina. We were interested in what parasites are found in these birds and whether any of the bobolink Plasmodium lineages match those found in Galapagos. This work was published in Conservation Biology and Ecology & Evolution.
Dissertation: Evolutionary ecology of hosts and parasites
Understanding population connectivity in hosts and parasites is instrumental in defining the scale at which coevolution may be occurring. In order to understand how and when parasites move between different hosts, I studied a seabird – Hippoboscid fly ectoparasite (and vector) – blood parasite system in the Galapagos Islands. Despite strong genetic differentiation between Galapagos frigatebirds and their conspecifics, we found no genetic differentiation in their Haemoproteus blood parasite (Levin et al. 2011). This suggested that the movement of the Hippoboscid fly vector could facilitate large-scale movement of the blood parasite. To test this, I completed a comparative population genetic study of Galapagos great frigatebirds, Nazca boobies, and their respective Hippoboscid fly parasites. I found high levels of gene flow in both fly species, despite marked differences in the degree of population genetic structure of their bird hosts (Levin and Parker 2013; Levin and Parker 2012). This suggests that host movement, (and therefore parasite movement), is not associated with host breeding dispersal and that hosts are moving more than we previously thought. Finally, I examined within-colony transmission of the blood parasite between frigatebird and fly hosts. I inferred host-switching by analyzing frigatebird genotypes amplified from the fly gut. This allowed me to identify host genotypes in bloodmeals that did not match the host from which the fly was collected. Flies infected with the blood parasite were less likely to host switch, suggestive of a cost of parasitism for the fly (Levin and Parker 2014). Collectively, this research showed that by adding information on parasites to population genetic studies we uncover hidden detail in host population connectivity.
Undergraduate research: Song in Savannah sparrows
For my undergraduate honors project, I studied song behavior in an island population of Savannah sparrows (Passerculus sandwichensis), working with Dr. Nathaniel Wheelwright from Bowdoin College, my alma mater, and Dr. Corey Freeman-Gallant, from Skidmore College. I investigated the changes in songs over several decades, using recordings that had been made on Kent Island since the 60s. Additionally, I investigated whether bill morphology constrained song in any way and whether singing rate was related to a male's paternity - both in guarding his own paternity and gaining access to neighboring females. We have published two papers from this work (Wheelwright et al., 2007; Williams et al., 2013). Here's a clip from Scientific American featuring our work on cultural evolution of song!