Education Postdoc 1992-94 Hebrew University of Jerusalem, Israel. (with Avi Shmida) Postdoc 1990-92 University of California at Santa Barbara. (with Susan Mazer) Ph.D. 1990 University of Illinois. (advisor = May Berenbaum) M.Sc. 1985 University of Toronto. (advisor = Spencer Barrett) B.Sc. 1981 McGill University

My research program focuses on plant evolutionary ecology and biological invasions. I am interested in how natural selection, resulting from positive interactions (eg: plant-pollinator) and negative interactions, (eg: plant-pathogen) influences patterns observed in various species of angiosperms. I currently have an active lab of undergraduate and graduate students who are working on a diversity of topics. This research is conducted in the Georgia's coastal plain, the University of Virginia's Mountain Lake Biological Station, and in Europe.

Ecological Genetics of Plant Invasions

Owing to their ecological and economic costs, a primary goal of research on alien species is to understand the factors responsible for successful invasion. It is commonly noted that individuals in the introduced part of a species' geographic range exhibit increased vigor when compared to plants in the native range. This pattern could arise if ecological conditions in the new environment are different from the native range (e.g., absence of natural enemies). Alternatively, differential performance could arise from genetic changes following invasion. The goal of my research is to examine ecological and genetic aspects of the successful invasion of Silene latifolia into North America from Europe.

Floral Polymorphisms and Pollination Biology

Hermaphroditic flowers disseminate and receive pollen. As a result of this duel function, flowers represent a compromise in selection pressures that operate on male and female function. My studies on temperate, desert and tropical plant-pollinator systems have focused on how intrapopulation variation in floral morphology influences male and female function. I am currently examining the fitness consequences of two variable floral traits (color and size) in Linaria canadensis, an annual plant in Georgia. Another project deals with pollination specialization and testing the validity of the pollination syndrome concept. This study focuses on the large group of morning glory (,i>Ipomoea) species that grow sympatrically in the southeastern coastal plain.

Evolutionary Ecology of Flower Size Variation

Flowers are the unit of reproduction in plants and the way they are constructed has a strong influence on how successful they are in donating (male function) and receiving (female function) pollen. It is easy to see that any variation in either the size or morphology of a flower can directly impact the pollination process. Despite the potential importance of variation in the size of flower parts to plant reproductive success, very little attention has been paid to quantifying just how much variation does exist in flower size in natural plant populations. I have been focusing on whether the extent of variation in flower size is related to attributes of a species' floral architecture (ie: radial vs. bilateral symmetry) and pollination syndrome. For example, has natural selection eroded the amount of phenotypic variation in the size of flowers in species that are pollinated by animals compared to wind-pollinated taxa?

Feeding Specialization in Parasitic Plants

Although the vast majority of plants are autotrophic and carry out photosynthesis, there exists a small group of flowering plants that receive their carbohydrates by parasitizing other plants. Over time, several different types of parasitic strategies have evolved: some plants connect directly into the roots of their hosts while others tap into the fungi that form ectomycorrhizal associations with host plants. In collaboration with Rytas Vilgalys (Botany, Duke University) I have been exploring some basic aspects of the ecology, population biology and molecular genetics of Indian Pipe (Monotropa uniflora, Ericaceae) at Mountain Lake Biological Station. Given that there can be hundreds of species of fungi in the soil, we are interested in how Indian Pipe selects the fungus species to infect. Are they using all the mycorrhizal species randomly or are they choosy? In other words, are they generalists or specialists?

The Consequences of Fungal Galls on Flame Azalea, a Native Appalachian Tree

Along with Dr. Leslie Rissler (University of California, Berkeley) I have been addressing questions concerning the evolutionary ecology of disease caused by fungal pathogens. We have been working at the Mountain Lake Biological Stationwith Flame Azalea (Rhododendron calendulaceum), a native tree found in the forest understory in mountains of the southeast US. Prior to flowering the inflorescences that produce orange-yellow flowers are sometimes infected by large galls formed by a fungus. The Flame Azalea galls can attain the size of small apples and are formed by the fungus Exobasidium vaccinii, a disease common to members of the plant family Ericaeae. We are examining whether: 1) the presence of fungal galls has any effect on the growth and reproduction of the host Flame Azalea tree; 2) is there variation in the occurence or intensity of disease among different populations, or between individuals within a single population? If there is variation in disease prevalence, then are there plant or population traits (eg: plant size, density) that may explain these patterns?

Environmental Biology
This course is designed to introduce non-major students to contemporary issues of environmental biology.

Evolution
This undergraduate/graduate level course presents an introduction to the world of evolutionary biology in which we explore the history of evolutionary thought and how the major evolutionary forces (natural selection, genetic drift) generate change at various levels of organization.

Scientific Presentation
This course is designed to give graduate students practical experience in writing research proposals and presenting oral presentations.

The Research of Charles Darwin
This graduate-level seminar examines the breadth of Darwin's research contributions by reading parts of his books.

Brandy Penna. Pollination limitation in European and North American Silene latifolia.

Lindsay Heaton. 2004. The role of hybridization in a biological invasion.

Amy Blair. 2003. Evolutionary processes in a biological invasion: an experimental study with Silene latifolia.

Daniel Parrish. 2002. Ecological genetics of plant invasions.

Dexter Sowell. 2001. Testing the concept of pollination syndromes using Ipomoea spp.

David Abbott. 2000. Consequences of flower size variation in four sympatric Ipomoea species.

Andrea Whatley. 1999. The ecological and evolutionary dynamics of floral polymorphisms in Linaria canadensis.

• David Abbott - Seed size variation in Ipomoea coccinea and I. quamoclit.
• Micheal Anglin - Prey capture rates in carnivorous pitcher plants.
• Brooke Brandenburg - Gender-based differences in the use of cell phones in Homo sapiens
• Jada Carter - A comparison of flower traits between European and North American populations of an invasive plant.
• Brian Davis - Pollinator faunas of four morning glory species.
• Wendy Denton - Floral polymorphisms in Linaria canadensis.
• Christina Dulock - Pollinator choice at a floral buffet of morning glories.
• Abraham Freiji - The evolution of mating incompatibility in an invasive plant
• Christina Futch - A systematic cleanup of confusing Ipomoea species.
• Lisa Goolsby - Distyly in Israeli populations of Linum mucronatum.
• Kristin Kelly - The relationship between population size on sex ratios in Rumex.
• Joanne Kendrick - Sex ratios in dioecious populations of Rumex.
• Emily Kuhnlein - Effect of seed morphology on dispersal in pines.
• Nadine Lebedick - Nectar production in four morning glory species.
• Erin Merritt - The influence of life history variation on allocation strategies in morning glories.
• Katrina Motes - Prey capture rates in pitcher plants.
• Colleen Murphy - Morph frequencies in polymorphic Linaria canadensis.
• Chris O'Neil - Do pollination syndromes exist? Testing the dogma with a suite of Ipomoea species.
• Brent Paige - Herbivory on the flowers of four morning glory species.
• Catherine Prior - Nectar production in the floral morphs of Gelsemium sempervirens.
• Jeremy Rayfield - Population variation in morph frequencies in the distylous Gelsemium sempervirens.
• Susan Sellers - Floral polymorphisms in Linaria canadensis.
• Becky Smyth - Distyly in Israeli populations of Linum mucronatum.
• Kimberly Stewart - Seed size variation in Ipomoea coccinea and I. quamoclit.
• Paul Uribe - Phenological flowering patterns in sympatric morning glories.

Department of Biology, Georgia Southern University

last modified: 6/30/08