Scott Villa
Post Doc

(801) 585-9742


I am an evolutionary biologist and parasitologist broadly interested in understanding the fundamentals of parasite diversification.

I graduated with a B.A. in Ecology and Evolutionary Biology from the University of Colorado, Boulder in 2008. There, I was exposed to the complex world of parasites and became fascinated with host specialization and parasite manipulation. Specifically, I wanted to know how parasites evolve to exploit the ecology and life history of their hosts.

Since coming to the Clayton-Bush lab at University of Utah I have focused on developing an innovative system for tracking parasite adaptations to novel hosts in real time. Unlike many other host-parasite systems, we are able to start with a single parasite lineage and track both the phenotypic and genotypic changes that underlie adaptation and diversification in divergent ecological environments. Ultimately, I am interested in the origin and types of changes that underlie the evolution of reproductive isolation. I hope that by understanding how selective forces influence parasite microevolution, we can begin to appreciate the processes that have allowed parasites to become so incredibly successful and diverse.


Study organism

My research focuses on a well-studied parasitic feather louse, Columbicola columbae. This species primary infests rock pigeons (Columba livia), but has also been found on other species of pigeons and doves. C columbae completes all stages of its life cycle, including reproduction, on the body of its host. Thus, mating is more likely to happen between lice on the same host species than between lice on different host species. This degree of inherent isolation may facilitate adaptive differentiation by reducing gene flow between populations occupying different host individuals or species. In this way, the pigeon-louse system mimics island systems, making it an ideal model for studying adaptive evolution and ecologically driven speciation.

Experimental evolution of parasite body size

Like many other parasites, the size of lice is positively correlated with the size of their host. I am interested in experimentally recreating this host-parasite relationship across a range of host sizes to understand how lice evolve to exploit different sized hosts. Fortunately, domesticated rock pigeons have been artificially selected for dozens of extreme phenotypic characteristics, including body size. By using different sized breeds of C. columbae’s native host, I am able to manipulate host size to examine the impact on parasite phenotype.

Ecological speciation

I may be the only person in the world interested in louse sex. My recent research has suggested that louse body size plays an important role in reproductive compatibility among conspecific populations of C. columbae. This has led me to explore the mechanics and sexual preferences involved in louse reproduction to ask how reproduction might be affected by the evolution of differences in body size in response to selection imposed by different sized hosts. The evolutionary mechanisms explored in my research lie at the heart of ecological speciation and an ultimate goal of my work is to understand how reproductive isolation could evolve via divergent natural selection.


My time spent in Colorado and Utah has solidified my love for the mountains. I generally enjoy hiking, camping and being outdoors. I jump at every opportunity I get to travel. Although, now wherever I go in the world, I can’t help but notice the local pigeons…






Villa SM, Koop JAH, Le Bohec C, and Clayton DH. 2018. Beak of the pinch: anti-parasite traits are similar among Darwin’s finch species. Evolutionary Ecology PDF

Villa SM, Evans MD, Subhani YK, Altuna JA, Bush SE and Clayton DH. 2018. Body size and fecundity are correlated in feather lice (Phthiraptera: Ischnocera): Implication of Harrison’s Rule. Ecological Entomology DOI: 10.1111/een.12511 PDF

Sweet AD, Boyd BM, Allen JM, Villa SM, Valim MP, Rivera-Parra JL, Wilson RE and Johnson KP. 2017. Integrating phylogenomic and population genomic patterns in avian lice provides a more complete picture of parasite evolution. Evolution doi:10.1111/evo.13386. PDF

Boyd BM, Allen JA, Nguyen N, Sweet AD, Warnow T, Shapiro MD, Villa SM, Bush SE, Clayton DH and Johnson KP. 2017. Phylogenomics using target-restricted assembly resolves intra-generic relationships of parasitic lice (Phthiraptera: Columbicola). Systematic Biology doi:10.1093/sysbio/syx027. PDF

Villa SM, Goodman GB, Ruff JS and Clayton DH.  2016.  Does allopreening control avian ectoparasites?  Biology Letters 12: 20160362. PDF

Villa SM, Campbell HE, Bush SE and Clayton DH. 2016. Does anti-parasite behavior improve with experience? An experimental test of the priming hypothesis. Behavioral Ecology doi:10.1093/beheco/arw032. PDF

Bartlow A, Villa SM, Thompson MW and Bush SE. 2016. Walk or ride? Phoretic behavior of amblyceran and ischnoceran lice. International Journal of Parasitology 46: 221-227. PDF

Makarikov AA, Tkach VV, Villa SM and Bush SE. 2014. Description of two new species of Hymenolepis Weiland, 1858 (Cestoda: Hymenolepididae) from rodents on the Luzon Island, Philippines. Systematic Parasitology doi:10.1007/s11230-014-9528-x. PDF

Villa SM, Le Bohec C, Koop JAH, Proctor HC, and Clayton DH. 2013.  Diversity of feather mites (Acari: Astigmata) on Darwin's finches.  Journal of Parasitology, 99:756-762. PDF

Bush SE, Villa SM , Boves TJ , Brewer D, and Belthoff JR. 2012. Influence of bill and foot morphology on the ectoparasites of Barn Owls.  Journal of Parasitology, 98:256–261 PDF