Biology Faculty Research Interests
The current research interests or projects of the biology faculty, which include many opportunities for undergraduate participation, are described below.
Dr. Rachel Collins, Assistant Professor of Biology
B.S., North Carolina State University
M.S., Miami University
Ph.D., University of Pittsburgh
I use a theory driven approach to address applied questions in community ecology. My research program identifies the mechanisms controlling species composition and diversity using multi-factor, manipulative experiments. Forests are great model systems for tackling such issues because they are valuable to humans, are important components of global nutrient cycles, and house a great deal of diversity. Forests, however, are not always as they appear. Communities full of trees may seem healthy and sustaining when in fact they are losing native species, adding invasive species, have altered ecosystem function, and are unable to regenerate following disturbance. Consequently, simply identifying controlling mechanisms or ecological drivers may not be enough and be leading us to miss the forest for the trees. My research identifies the relative effects of drivers and characterizes their interactions. My goal is to develop conceptual models that more accurately depict forest dynamics and to use these models to develop effective management strategies for forest communities.
Currently, my research students and I are examining patterns of non-native invertebrates and invasive plants in the species rich forests of the southern Appalachians. We are examining how these non-native species interact with very abundant native species (particularly white-tailed deer) to shape native plant communities. We are testing several hypotheses (e.g., enemy release, novel weapons, apparent competition, etc) proposed to explain the success of invasive species. I suspect that each of the proposed hypothesis to explain invasive species success is operating in some species some of the time. My hope is to discover generalizable patterns in invasive species dynamics that will lead to more effective management of those invasive species that are having the greatest impacts on native plant and animal communities.
Dr. Brooks Crozier, Associate Professor of Biology
B.S., Roanoke College
M.S., Virginia Polytechnic Institute and State University
Ph.D., Virginia Polytechnic Institute and State University
My research interests have concentrated on the tracking of fecal bacteria in surface water (Bacterial Source Tracking or BST). Until recently we have been unable to identify the source of surface water fecal contamination. Standard filtration methods are used to obtain fecal coliform (E. coli) and fecal enterococci counts of water samples. However, cattle commonly frequent waterways as do ducks and other wildlife. Therefore, the source of this contamination cannot be determined by these methods alone. Antibiotic resistance analysis (ARA) has become the benchmark tool to predict the source of contamination, and has merit in this field of study. ARA, however, cannot predict the source, theoretically, as well as certain molecular biology methods may predict source. Most recently my student and I have developed a PCR based source tracking method which is currently being evaluated for commercial application. We have also started looking at specific bacterial genes which may help us determine the source from which the bacterium originated. We have sequenced genes from bacteria from different animal sources, looked for genetic differences, and will try to exploit these genetic differences to specifically develop a sequence-based bacterial source tracking method.
Dr. Darwin D. Jorgensen, Professor of Biology
B.S., Iowa State University;
M.S., University of South Carolina
Ph.D., Iowa State University
My research centers around a consideration of problems related to circulatory and respiratory function in a variety of different animals. At present, my research students and I are interested primarily in certain arthropods and molluscs. The general term that describes the kind of work we do is comparative physiology. As the term implies, we are interested in comparing how different kinds of animals solve similar physiological problems. The primary goal is to gain a better understanding of how these animals work. But I am also very much interested in relating the physiology of an animal to its lifestyle and natural habitat. In other words, what is it about how an animal works that allows it to do what it does and live where it does?
Most recently, we have been studying cardiovascular and respiratory function in the American lobster, Homarus americanus and the blue crab, Callinectes Sapidus. Lobsters and blue crabs are migratory and are known to walk considerable distances along the ocean (or river) bottom. My students and I have been investigating how the cardiovascular and respiratory systems in these arthropods respond to controlled bouts of underwater walking. In our experiments, we monitor a variety of physiological parameters (such as blood pressure and the extraction of oxygen from ventilatory water by the gills) before, during and after an exercise period. From this work, we are developing a picture of how the cardiovascular and respiratory systems work together in these commercially-important arthropods to deliver oxygen to the tissues under stressful conditions.
We have also become interested in characterizing the physiological effects of bacterial infection in blue crabs, focusing on post-infection alteration of gill function. We hope to extend this work to lobsters as bacterial infections can profoundly impact naturally-occurring populations of both crustaceans in fisheries areas.
Dr. Christopher S. Lassiter, Associate Professor of Biology
B.S., Furman University
Ph.D., Duke University
My research interests lie in the field of developmental biology. The mechanisms by which a single cell can give rise to a complex organism have always amazed me. Cells must differentiate and signal to each other, turning on vast networks of genes while coordinating growth, shape, and function. Much research has been done on small range signaling molecules during development. During my graduate work, I became interested in molecules that signal over longer ranges: hormones.
My work has focused on the estrogen signaling pathway. Estrogen is an important molecule in the developing embryo and in the adult vertebrate. This small molecule signals in many tissues of the body, including reproductive tissues, adipose, brain, bone, and heart. Estrogen signals by binding to estrogen receptors. My work has involved characterizing the estrogen receptors along with aromatase, the gene that codes for estrogen synthesis. The expression pattern of aromatase in the embryonic brain and its control by steroid hormones is well conserved among vertebrates. The pleiotropic effects of estrogen in the developing brain could affect neural architecture resulting in morphological and behavioral effects well into adulthood.
Dr. DorothyBelle Poli, Associate Professor of Biology
B.S., University of Pittsburgh
Ph.D., University of Maryland
I enjoy exploring how a physiological process evolved into the process that is taught in textbooks. For example, my Ph.D. dissertation looked at the role of polar auxin transport on the development of the sporophyte body axis. Future experiments would continue the classification of polar auxin transport in sporophytes, but more importantly, I want to explore polar auxin transport across gametophytic structures since the current literature is not normalized, contains many gaps, and therefore, evolutionary generalizations cannot be drawn.
The movement of plants from the water to the land created the need for plants to become larger and more erect in order to compete for light. This transition resulted in the evolution of vascular tissue, stomata, guard cells, and the cuticle. My goal is to examine these features across the extant plants to begin to fill in the evolutionary relationships between the physical changes and the physiological processes.
My research goal is to use these projects as a training platform for undergraduates who are interested in research or who desire preparation for their graduate studies. Both of these projects have the capacity to offer a broad research experience for undergraduates, including exposure to morphology, anatomy, molecular biology, bioinformatics, biochemistry, evolution, and physiology. Also, these projects have aspects that will require collaboration with other scientists, and this experience is one that many undergraduates do not get in traditional research internships and interactions. Developing research projects that ask broad questions gives an undergraduate a research experience that teaches them scientific theory and critical thinking while they learn the basics of the scientific material. These projects are broad enough to allow a student to take them in directions that drive their interests as well as mine.
Dr. Steven Powers, Assistant Professor of Biology
B.S., Georgetown College
M.S., Eastern Kentucky University
Ph.D., University of Alabama
My primary research interest is the evolution of stream fishes of the southeastern United States and the ecological and historical variables that have influenced and continue to influence them. Not only are fishes inherently interesting due to their high level of diversity, range of evolutionary novelties, and varied ecologies, they are also excellent model organisms for investigating evolutionary processes. For many fishes, confinement to small streams and low dispersal capability provide a natural setting for investigating modes of speciation and biogeographic patterns Dramatic sexual dimorphism present in several groups of fishes also indicates that sexual selection has played a major role in their evolution. Furthermore, the physical pressures of living in stream habitats have influenced the evolution of stream fishes and the communities to which they belong.
My research has studied and continues to study evolution, biogeography, systematics, ecology, and conservation of freshwater fishes of the southeastern United States. To address such a wide variety of topics, I have employed many techniques, including assessments of genetic differentiation, molecular and morphological phylogenetic systematics, quantifying stream habitat and community structure, forming and testing biogeographic hypotheses, and quantifying life history characteristics. One of the strengths of my research program is a strong working knowledge of my study organisms, the communities to which they belong, and streams of the southeastern United States. By working in similar systems, with similar species, I gain a more solid foundation from which to build hypotheses about the processes influencing the evolution of my study organisms. These hypotheses can then be tested and modified by continual addition of data and further analyses. By developing more refinded hypotheses of evolutionary patterns, I am able to develop more refined hypotheses of evolutionary processes. This leads to reciprocal illumination of evolutionary questions and forms a cornerstone of my research program.
Dr. Leonard D. Pysh, Professor of Biology
A.B., Wabash College
Ph.D., University of California, San Diego
All living organisms consist of one or more cells. The shapes and sizes of cells are so faithfully reiterated from generation to generation that they can be used to distinguish species within unicellular organisms and cell types within multicellular organisms. This faithful reiteration of cell shape indicates that cell shape is largely determined by the molecular genetic mechanisms. Interestingly, very little is known about the molecular mechanisms by which cell shape is determined.
In my lab, we use the simple plant Arabidopsis thaliana to study root cell shape. Arabidopsis has become a model plant as a result of its small size, its simple morphology, its rapid generation time, and its small genome. Mutations that affect the shape of the cells in the root have been identified, and a number of the genes at these loci have been isolated. The simple hydrocarbon ethylene is also known to have a profound impact upon root cell shape. Biochemical and genetic studies indicate that the cell shape genes and the ethylene perception/response genes interact to determine the final shape of cells in the root. The focus of my research is to understand the roles of these two classes of genes in cell shape determination, using a combination of genetic, cellular, and molecular techniques. We have identified a number of plants that have aberrant root cell shape and ethylene responses and are using a variety of molecular tools to study both of these classes of mutants.
Dr. Marilee A. Ramesh, Associate Professor of Biology
B.S., University of Wisconsin-Stevens Point
Ph.D., Indiana University
An underlying feature of the biological sciences is the assumption that all life has evolved from a single ancestor. The diversity of life we see all around us is even more amazing when we consider that each organism is in some way related to the others. Resolving those relationships has been a major focus of evolutionary biology.
I am interested in studying the origins and evolution of the process of meiosis. Meiosis is a specialized form of cell division that produces reproductive cells, such as eggs and sperm in mammals, megaspores and pollen in most plants and spores in fungi. Meiosis is absent in bacteria. It is a process that occurs only in eukaryotic organisms (animals, plants, fungi and protists), but it is not known whether meiosis occurs in all eukaryotes. When meiosis first originated and how it has evolved throughout the eukaryotic lineage are two largely unanswered questions. Much of what we know about meiosis is limited to studies using animal, plant or fungal model systems. However, protists are by far the most informative group in which to study the evolution of this process among eukaryotes. Protists represent not only the greatest number of species but also exhibit the greatest variation among the four major groups of eukaryotes. However, until recently, these single-celled eukaryotes have been difficult to work with as laboratory model systems.
Recent technological advances in the area of genomics and bioinformatics have enabled us to begin unraveling the mysteries of protist meiosis. The genomes of many protists, particularly those species that are the causative agents of diseases such as malaria, sleeping sickness, and intestinal discomforts are currently being sequenced. Strategies much like those used to sequence the human genome are being applied to these organisms. In my research laboratory, we make use of the data collected from these sequencing projects by searching or "mining" them for the specific meiotic genes we are interested in studying. Questions I am interested in are i) whether a species has all the genetic information necessary to perform meiosis, and if so, ii) are these genes expressed, iii) are the gene products functional and iv) how have these proteins changed throughout the course of eukaryotic evolution. Projects in my lab involve a combination of computational analysis and the application of molecular biology techniques to study elements of the genome of certain protists. In connection with this, I am interested in culturing local protist species and including them in these analyses.
Roanoke College students hope the results of a green roofs study would reduce rainwater runoff at some of downtown Roanoke's buildings and save energy costs for the city.