David K. Skelly

I am an ecologist interested in the dynamics and fate of animal populations and communities. My research program is organized around two primary themes:

Emerging Diseases. Limb deformities of amphibians are a well described emerging disease phenomenon of uncertain cause. The leading hypothesis has been an infectious agent Ribeiroia, a trematode parasite. Our work in Vermont, an epicenter for amphibian deformities, shows that high rates of limb deformities can occur in the absence of Ribeiroia requiring an alternate mechanism such as chemical pollutants. We are building on this research in collaboration with Gunter Wagner (EEB). A pilot grant from the Yale Medical School is enabling us to gather initial data exploring the genetic basis for abnormal limb development in the presence of chemical pollutants. Our initial results suggest that genome wide expression patterns (using gene-chip technology) will provide an excellent basis for understanding the causes of abnormal development. A complementary project explores the role of urbanization in promoting infectious disease in wildlife. A survey of Connecticut wetlands shows that amphibians living in urban areas can suffer intense kidney infections. These outbreaks by echinostome trematodes are previously unrecognized and potentially debilitating to urban wildlife.

Population Responses to Dynamic Landscapes. Human activities lead to rapid changes in landscapes across much of the Earth’s surface. In the freshwater wetlands I study, one of the most profound effects is the change in forest structure in and around wetland basins. Either by directly removing trees, controlling beaver populations, or suppressing fires the canopy cover over ponds can be dramatically affected and rapidly changed. We have shown that amphibian populations are sensitive to such changes. Population extinctions are one common response. More recently we have discovered that one of our study species, the wood frog, is capable of rapid evolutionary response to changing temperature altered by canopy removal or regrowth. This surprising finding in a vertebrate implies that responses to other thermal changes, such as those associated with climate change are possible and even likely. The recognition of evolved response could greatly influence estimates of the ecological consequences of climate change.

Teaching ecology involves the difficult task of supporting students in their attempts to connect abstract concepts with elements of the natural world.  A successful ecology course is one in which students learn to see beyond Animal Planet vignettes of organisms eating each other to the broader consequences of those interactions and the myriad others that would escape our notice if we were not trained to look for them.  I teach two primary courses at Yale, landscape ecology and aquatic ecology.  In both, I challenge students to link the attributes of particular systems with the ways in which ecologists conceptualize the natural world.  My goal is to provoke them into thinking about (1) why we need such concepts, (2) what are the tradeoffs encountered when comparing among concepts and models, (3) how are concepts and models translated into robust and testable predictions, and (4) how do we wade out into the natural world and figure out what to measure and how to interpret what we have measured.

As a practical matter each course involves tradeoffs of its own.  Landscape ecology is a large, introductory level lecture course in which I employ Web-based lab exercises (http://www.cbc.yale.edu/people/skelly/teaching.html).  I try to engage students in the many ways that we can conceive of ecological patterns and then to consider the challenges inherent in studying large scale patterns.  There are good reasons why ecologists have tended to look at smaller scales.  During the course, the students learn about a variety of attempts to overcome the difficulties in working at large scales (e.g., island biogeography, cellular automata, spatially explicit, individual based models).  Students interact with the natural world primarily by completing a term project in which they are encouraged to develop a hypothesis and test a prediction using meta-analysis.  The projects have turned out to be a remarkably successful way to get students engaged as scientists.  In addition, for particularly motivated students, they have yielded an opportunity to do publishable quality research.  In five years of teaching this class three students have produced papers that have been or will be published in peer-reviewed journals.

By contrast, aquatic ecology is a much smaller, upper level class with a heavy emphasis on field instruction.  I am fortunate to have access to two field sites with a wealth of historical data.  Students spend the first half of the course sampling Linsley Pond where G. Evelyn Hutchinson and his students worked for many years beginning in the 1930's.  Students learn theory, some of which was at least partially inspired by work in Linsley (e.g., Size-Efficiency Hypothesis), and they learn sampling techniques all while adding to a long-term historical record of information.

During the second half of the course, we work in a small watershed where Herb Bormann, developer of the Hubbard Brook Project and now an emeritus professor, has lived for over 30 years.  We add to background data collected by his former students to evaluate two small order streams.  Students learn to measure physical and chemical characteristics of streams and how to sample and identify macroinvertebrates.  One of these streams is in a largely undeveloped subwatershed while other was subjected to a housing development in the 1970's.  Students use their own and historical sources to chart the divergence in characteristics of these streams.

Feedback from students in the form of course evaluations and teaching awards suggests that these courses have been effective.  While I am very comfortable with the subjects I have been teaching at Yale, I recognize that there are likely to be different needs at different institutions.  I am prepared to teach any of a variety of ecology or conservation related topics as well as field and taxonomy based courses (e.g., herpetology).