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Faculty and Staff

Felicia Keesing Professor of Biology; David and Rosalie Rose Distinguished Professor of Science, Mathematics, and Computing; Director, Biology Program

Office: Reem-Kayden Center 211
Phone: 845-752-2331
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Ph.D., Integrative Biology (1997), University of California, Berkeley
B.S., Symbolic Systems (1987), Stanford University


Biodiversity, Ecology and Evolution, Sex and Gender, Ecology of Infectious Diseases

Scientific Research

My primary research program is based at the Cary Institute of Ecosystem Studies in Millbrook, NY. Together with my colleague, Rick Ostfeld, I am investigating how the risk for humans of contracting Lyme disease is influenced by interactions among forest vertebrates, the causative agent of Lyme disease, and its vector, the blacklegged tick (Ixodes scapularis). Lyme disease is caused by a bacterium (Borrelia burgdorferi) which is passed between hosts through the bite of an infected tick. Hosts vary in their ability to infect ticks, or their reservoir competence. For example, white-footed mice (Peromyscus leucopus) transmit the Lyme bacterium to 90% of ticks that feed on them; they have extremely high reservoir competence. On the other hand, very few ticks that feed on deer (Odocoileus virginianus) pick up the infection, even if the deer are infected. Ostfeld and I have developed a conceptual model called the dilution effect, which suggests that when the diversity of hosts for ticks is high, Lyme disease risk is low, because the presence of a rich assemblage of hosts dilutes the impact of the high reservoir competence of white-footed mice. Together with a summer undergraduate research student, Brian Allan, we have demonstrated that the fragmentation of forest into small patches causes a dramatic increase in Lyme disease risk because non-mouse hosts disappear from small areas of forest, a study that appeared in Conservation Biology. Together, these results demonstrate that biodiversity and the preservation of intact forests can protect human health.

My research on Lyme disease is supported by grants from the National Institutes of Health, with Ostfeld and several other collaborators, including Ken Schmidt (Texas Tech University) and Kathleen LoGiudice (Union College).

I am also a co-director of the Research Experiences for Undergraduates (REU) program at the Cary Institute of Ecosystem Studies in Millbrook. This program, which has been running since the inception of the REU program by NSF, is characterized by its emphasis on the social contexts in which ecological research takes place. In addition to conducting their own individual projects, students in this program conduct a group investigation into an ecological issue with societal implications (e.g. PCBs in the Hudson River, control of West Nile Fever virus), develop an ecology experience for underprivileged kids, explore alternative careers in ecology through a day-long career forum, and have regular workshops and roundtables on other issues. I have mentored students in this program each summer for a number of years, and I assist in the oversight, assessment, and development of the program itself

Selected Publications

  • Keesing, F. 1998. Impacts of ungulates on the demography and diversity of small mammals in central Kenya. Oecologia 116:381-389.
  • Keesing, F. 2000. Cryptic consumers and the ecology of an African savanna. BioScience 50:205-215.
  • Ostfeld, R.S. and F. Keesing. 2000. Biodiversity and disease risk: the case of Lyme disease. Conservation Biology 14(3): 1-7.
  • Ostfeld, R.S. and F. Keesing. 2000. Pulsed resources and community dynamics of consumers in terrestrial ecosystems. Trends in Ecology and Evolution 15: 232-237.
  • Ostfeld, R.S. and F. Keesing. 2000. The function of biodiversity in the ecology of vector-borne zoonotic diseases. Canadian Journal of Zoology 78:2061-2078.
  • *Shaw, M.T., F. Keesing, and R.S. Ostfeld. 2002. Patterns of predation on Acacia seedlings in an African savanna. Oikos 98(3): 385-392.
  • *Allan, B.F., F. Keesing, and R.S. Ostfeld. 2003. The effect of habitat fragmentation on Lyme disease risk. Conservation Biology 17:267-272.
  • LoGiudice, K., R.S. Ostfeld, K. Schmidt, and F. Keesing. 2003. The ecology of infectious disease: Effects of host diversity and community composition on Lyme disease risk. Proceedings of the National Academy of Sciences 100: 567-571.
  • *Shaw, M.T., F. Keesing, R. McGrail, and R.S. Ostfeld. 2003. Factors influencing the distribution of larbal blacklegged ticks on rodent hosts. American Journal of Tropical Medicine and Hygiene 68:447-452.
  • Ewing, H., K. Hogan, F. Keesing, H. Bugmann, A. Berkowitz, L. Gross, J. Oris, and J. Wright. 2003. The role of modeling in undergraduate education. Pages 413-427 in: C.D. Canham and J. Cole, eds., Models in Ecosystem Science. Princeton University Press.
  • Goheen, J., F. Keesing (corresponding author), B. Allan, D. Ogada, and R.S. Ostfeld. 2004. Net effects of large-mammal exclusion on Acacia seedling survival in an East African savanna. Ecology 85:1555-1561.
  • Ostfeld, R.S., P. Roy*, W. Haumaier, L. Canter, F. Keesing, and E. Rowton. 2004. Sandfly (Lutzomyia vexator) populations in upstate New York: abundance, microhabitat, and phenology. Journal of Medical Entomology 41(4): 774-778.
  • Ostfeld, R.S. and F. Keesing. 2004. Oh the locusts sang, then they died. Science 306:1488-1489. [Perspective]
  • Keesing, F., R.D. Holt, and R.S. Ostfeld. 2006. Effects of species diversity on disease risk. Ecology Letters 9: 485-498.
  • Dobson, A., I Cattadori, R. Holt, R.S. Ostfeld, F. Keesing, K. Krichbaum, J. Rohr, S.E. Perkins, and P.J. Hudson. 2006.  Sacred cows and sympathetic squirrels: the importance of biological diversity to human health.  PLoS Medicine 3(6) e231.
  • Keesing, F., R.S. Ostfeld, V.T. Eviner. 2008. Introduction. Pages 1-5 in Infectious Disease Ecology: Effects of Ecosystems on Disease and of Disease on Ecosystems, edited by R.S. Ostfeld, F. Keesing and V.T. Eviner. Princeton University Press.
  • Ostfeld, R.S., F. Keesing, and V. T. Eviner. 2008. Infectious Disease Ecology: Effects of Ecosystems on Disease and of Disease on Ecosystems. Princeton University Press.
*undergraduate students