Henry M. Wilbur

Research

Forest History

Henry and Becky are interested in understanding the land-use history and current forest dynamics on the station and other areas on Salt Pond Mountain. This area was logged, burned and pastured in the late 1800s and greatly affected by the chestnut blight in the 1930s. Currently the forested slopes are dominated by Northern Red Oak (Quecus ruber) with a fairly diverse group of canopy and understory trees. Our approach uses sample plots and a over five thousand marked trees to estimate forest composition, growth and mortality. We mapped the core plot in 1984. We also do a lot of dendrochronological (tree-ring) work in this system, partly because local weather records are available for over a century. This project addresses questions about long-term forest change and sets the stage for future studies of the effects of global change and local environmental disturbances. Katie Burke’s dissertation research is related to this project. The chestnut and striped maple projects overlap with this umbrella project.

Chestnut Epidemiology

The American chestnut (Castanea dentata) is now part of tri-trophic host pathogen system with the chestnut as the base, its fungal parasite Cryphonectria parasitica as the agent of its demise, and a double-stranded RNA virus of the fungus as a possible biological control agent. The chestnut persists as old genotypes that sprout from their root collars and grow for a few years to half a century before hey are killed by the fungus. Our interest is in the shoot demography and the relative importance of competition, disease, and browsing by deer on the fate of shoots. In 1996 we individually tagged nearly 5000 chestnut shoots on a 1 ha plot. The disease state and mortality of all shoots was monitored in 1997, 1998, 1999 and 2003. A subset has been followed annually since 2003. Amy Milo’s master’s thesis is related to this project.

Striped Maple Demography

Striped maple (Acer pensylvanicum) is a weedy understory tree with environmental sex determination (ESD) in which an individual may switch between being vegetative, male or female between years. In 1991 Miles Silman and I tagged about 1000 individual trees near a canopy gap created by Hurricane Hugo September 22, 1989. I have been following the growth, mortality, and sex expression of these stems and looking for new recruits ever since. I have also been interested in a foliar fungal pathogen, Rhytissma punctata, that I thought might influence sex expression. My current interest is to try figure out the adaptive nature of ESD from this nearly 20-year dataset.

Life History Theory

I have had a long interest in the evolution of demographic parameters, such as survival, breeding frequency, clutch size, and body size. Two recent projects that are still being finished address these issues in rather different systems.

Don Church did his dissertation on the metapopulation ecology of the 16 species of amphibians that visit a complex of 22 natural sinkhole ponds. The main study included a large capture-recapture study of the mole salamanders (Ambystoma opacum, A. maculatum, and the state endangered A. tigrinum) associated with three ponds that were completely fenced so that all adults could be captured as they entered and left the breeding ponds. This work involved extensive collaborations with biostatisticians and the USGS Wildlife Research Center in Patuxent, Maryland that resulted in some new methods for the analysis of capture-recapture data. We also developed novel software to recognize individuals from digital images of their spot patterns. My current question is how are three species that breed in the same ponds and live in the same forest coexisting with different life histories.

Patrice Ludwig did her dissertation on the metapopulation ecology of Forked Fungus Beetles (Bolitotherus cornutus), a tenebionid that spends its life on brackets of fungi, primarily Ganoderma applanatum. This is a tri-trophic system with the fungus exploiting dead trees (primarily oaks) and the beetle exploiting the fungus. Patrice is interested in the role of dispersal in population dynamics and the role of sexual selection in dispersal. I am focusing on the tri-trophic aspect of the system because I am getting data on long-term tree mortality from our work on forest dynamics.

Amphibian communities

My own work during the “Duke Years” was on the structure and function of food webs in temporary ponds. This program combined fieldwork in the Sandhills of North Carolina with experimental studies in an array of 144 artificial ponds that I built at Duke. This work is reviewed in Wilbur (1996).

At Virginia I have maintained an interest in amphibians, mostly vicariously through collaborations with my former and current students. My collaboration with Don Church is outlined above. My work at Mountain Lake Biological Station has included many studies of the red-backed salamander Plethodon cinereus and species that live in headwater streams. Kristine Grayson has also drawn me back into studying newts, Notophthalmus viridescens.

Teaching

Population Ecology

This class is aimed at students who have taken either ecology (EVSC 320) or Ecology and Evolution (BIOL 302) who have an interest in graduate study or employment in the broad fields of conservation biology, ecology, evolution, environmental law or policy. A course in differential calculus is required the basic mathematical skills are used in class. My goal in lectures is to teach the theory that underpins the application of population dynamics and species interactions to conservation problems. The students form project groups that focus the class on a single area of conservation biology during the last third of the course.

Ecology and Evolution

I teach the ecology third of this core course required of all biology majors. I try to teach the basic concepts of ecology that form the context in which evolution occurs. I take G. E. Hutchinson’s analogy of the “Ecological Theater and the Evolutionary Play” rather literally. I use a mathematical approach, but I also try to impart an appreciation of natural history and respect for the scientific way of knowing.

Population Biology Seminar

Janis Antonovics and I joined our groups into a weekly seminar to serve as a forum for our students to get some breadth in evolutionary ecology and ecological genetics and to help each other with research ideas and strategies. This group has continued at Virginia and meets every Wednesday afternoon that classes are in session. The current group has about six faculty, a several post-docs, about 15 graduate students, and several precocial undergraduates with frequent visitors from Environmental Sciences and other departments. We have outside speakers a couple of times a semester, but usually a graduate student is presenting their research proposals, progress reports, or practice job seminar. The seminar if followed by a happy hour for those who do that sort of thing.

Forest Ecology

Becky and Henry Wilbur teach a course is designed to help students learn the natural history of the habitats and organisms of southwestern Virginia through fieldtrips. We also teach how to study the population and community of forest trees using techniques such as surveying, sampling, dendrochronology, growth analysis, and community reconstruction. Students are expected to engage in vigorous fieldwork often in rugged terrain and not always beautiful weather. All fieldwork is aimed at answering a conceptual question about how forests work.

Field Entomology

For many years I have joined with Gard Otis and Steve Marshall to teach a joint course with the University of Guelph that brings together about 15 Canadians and 10 “Virginians” in mid-May. The course is intense – all day every day from about 8 am until 10 pm or later. Students love it. Each student makes a collection and learns how to identify insects using taxonomic keys in Steve’s book. They also work on group field projects with Gard and me that test ideas in ecology or behavior.

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