Campus Notice: Most College offices will be closed beginning Monday, December 22 and will reopen on Monday, January 5. [ Get More Info ... ]
 

Dr. Chris Harbison

Dr. Chris HarbisonChristopherHarbison
Associate Professor

email: charbison at siena dot edu

B.A. Biology, Environmental Science Concentration, Carleton College (1999)
Ph.D. Biology, University of Utah (2008)

Courses
- General Biology I & II (Biol 110 & 120), and associated labs
- Writing and Research Skills for Biologists (Biol 190)
- Principles of Evolution (Biol 265)
- Ornithology (Biol 270)
 

Research
My research focuses broadly on the fields of evolution and ecology.  More specifically, I am interested in how community-level interactions influence species’ ecology and shape the selective landscape in which they evolve.  By examining community-level dynamics rather than focusing on the ecology of a single species, I aim to better understand questions central to evolutionary ecology such as: How can two competitors coexist over time if they use the same resources?  What factors determine whether a species evolves to be a specialist or a generalist?  To what extent do species interactions influence evolutionary patterns, such as local adaptation and speciation? 

To address these types of questions, I use hosts and their parasite communities as model systems.  Why parasites?  Parasitism is the most dominant lifestyle on earth: by many estimates, greater than 50% of all Earth’s diversity consists of parasites.  For example, humans alone are host to >100 species of parasitic arthropods, helminths and protozoa.  With such an immense presence, parasites can exert tremendous selective pressures on their hosts and greatly impact community dynamics.

Host-parasite systems also provide a practical model for studying community-level processes.  Even a single individual can host a diverse assemblage of parasites.  Furthermore, because the entire parasite community is essentially restricted to the host, multiple parasite communities can be easily reared and studied in relatively natural laboratory settings.

Recent research projects have focused on the ectoparasite community of pigeons and doves.  These birds are host to multiple species of feather-feeding lice, which compete for host resources.  Previous work by University of Utah colleagues demonstrated that one species of louse outcompeted other lice for resources…so how can the inferior competitors coexist?  Community dynamics appear to play an important role in mediating competition.  Namely, my students and I found that the inferior louse competitor uses other ectoparasites in the community to “hitchhike” rides to new hosts (a phenomenon known as phoresis—Fig. 1).  Essentially the inferior competitor is a superior colonizer of new hosts.  This simple parasite community provides rare empirical support for a “competition-colonization tradeoff” that may promote the coexistence of competing louse species.

 

CHfig1
Fig. 1. SEM of two wing lice attached to a hippoboscid fly (SEM by E.H. Burtt, Jr. and J. Ichida). 

Why are lice phoretic?  Currently, I am interested in exploring why louse species differ in phoretic “hitchhiking”, and examining the larger ecological and evolutionary ramifications of phoresis on host-parasite interactions.  By comparing phoretic and non-phoretic lice, I aim to determine specific adaptations that enable lice to locate fly carriers, attach to the carriers, and remain attached until the next host is reached.  Additionally, my students and I will continue to explore the broader impacts of phoresis on host-parasite ecology and evolution.  For example, we found that phoretic lice are able to colonize new host species to a greater extent than non-phoretic lice.  By providing a simple mechanism to reach new host species, phoresis may play a key role in determining host specificity (whether a parasite is a generalist or a specialist) and governing local adaptation to hosts.

 

Representative Publications (* indicates an undergraduate author) 

Harbison, CW & R Boughton*. Thermo-orientation and the movement of feather-feeding lice on hosts. Accepted; 2014; Journal of Parasitology.
 
Harbison, CW & DH Clayton. 2011. Community interactions govern host-switching with implications for host-parasite coevolutionary history. PNAS 108:9525-9529.
 
Clayton, DH, JAH Koop, CW Harbison, BR Moyer, and SE Bush. 2010. How birds combat ectoparasites. The Open Ornithology Journal. Supplement: Current Trends in Avian Parasitology 3:41-71.
 
Harbison, CW, MV Jacobsen*, & DH Clayton. 2009. A hitchhiker’s guide to parasite transmission: The phoretic behavior of feather lice. International Journal for Parasitology 39:569-575.
 
Bush, SE, CW Harbison, D Slager*, AT Peterson, RD Price & DH Clayton. 2009. Geographic variation in the community structure of lice on Western Scrub-jays. Journal of Parasitology 95:10-13.
 
Harbison, CW, SE Bush, J Malenke & DH Clayton. 2008. Comparative transmission dynamics of competing parasite species. Ecology 89:3186-3194.
 
Dale, C, M Beeton*, CW Harbison, T Jones*, & M Pontes. 2006. Isolation, pure culture and characterization of Candidatus Arsenophonusarthropodicus, an intracellular secondary endosymbiont from the hippoboscid louse-fly, Pseudolynchia canariensis. Applied and Environmental Microbiology 72:2997-3004.