Department of Biological Science

Biological Science Faculty Member

Robert O. Lawton Distinguished Professor
B.A., University of Pennsylvania, 1975Ph.D., Duke University, 1980
Graduate Faculty Status

Research and Professional Interests:

My research revolves around understanding how ecological processes drive evolutionary ones and, sometimes, vice-versa. My research is focused on how and why features of animals and plants vary from one population to another.  When this variation has a genetic basis, it represents the earliest stage in the adaptive generation of biodiversity.  This variation can also generate differences in local ecological processes, thereby creating correlated differences among locations in evolutionary trajectories and ecological relationships. 

For example, populations of Trinidadian guppies at higher elevations of mountain streams have diverged from those at lower elevations.  The higher population density and lower level of food per individual at higher elevations, which are the result of reduced predation pressure on guppies at high elevations, produce natural selection that favors different features in the higher elevation populations than those in the lower elevation populations.  At the higher elevations, selection favors guppies that mature later and larger than those at low elevations, forage less selectively, and consume more algae than guppies at lower elevations that experience higher predation pressure.  Through their differences in diet and the distribution of body sizes, these two phenotypes of guppies have different effects on the algae and invertebrates in their habitat and thereby cause a striking difference in community and ecosystem organization. 

I am particularly interested in the process of density-dependent selection.  For one reason, it offers an interesting challenge for understanding local adaptation. For example, changes in predation pressure from one population to another usually produce changes in numerical density as well.  This is obviously true in the guppy populations and ascertaining whether differences in predation pressure or differences in density were the driving force of selection was no easy task.  For another reason, evolution under density-dependent selection will usually minimize a population's susceptibility to the negative effects of increased density on population growth rate and thereby change population parameters like the carrying capacity and, perhaps, the stability of that population's numerical dynamics.  These changes will, in turn, affect other aspects of community and ecosystem organization.   

With one foot in ecology and another in evolutionary biology, I have guided students in a diversity of research projects. My graduate students have studied topics from the community ecology of Amazonian frogs to the population genetics of gag grouper, from the development of personalities in bluefin killifish to the prenatal conflict between mothers and offspring in the least killifish.  The common element in all of these projects is an immense curiosity about nature and the determination to find answers to important questions regardless of the path to those answers.

Postdoctoral Associates:

Graduate Students: