Evidence that evolutionary change can occur rapidly in response to altered environmental conditions requires that evolutionary processes be considered as causes for even short-term ecological change. This project will develop the methods needed to examine the roles of genetic variation and adaptation in plant community responses to changes in nutrient supply and disturbance. The project is based on a long-term ecological field manipulation; as changes in nutrient supply and the frequency of mowing cause changes in the abundance of individual species in the community, the potential exists for selection on traits affecting fitness. By developing methods to measure genetic change, the researchers will expand the current experiment to address two major ecological questions. First, do short-term ecological changes drive rapid evolutionary responses? Second, what role does genetic variation within and among species play in determining community diversity, composition, and responses to environmental change? The proposed research is both exploratory and risky. Undergraduate students will develop molecular markers without the benefits of a research laboratory where such work is routine. It remains unclear whether even strong selection caused by changing ecological conditions can result in genetic divergence in the face of gene flow among individuals and thus, one of the key questions upon which the proposal is based is risky. Finally, the extent to which genetic variation influences ecological processes, and particularly community assembly and the maintenance of diversity, is quite unknown, adding an additional risk to the proposed study.
The project extends a long-term ecological experiment that was initiated to enhance ecology education for undergraduates at Eastern Carolina University and to provide students with authentic experiences in ecological research conducted at realistic spatial and temporal scales. The experiment serves as a unifying theme in the ECU biology curriculum, currently providing training in ecology, field methods, botany, experimental design and statistics. The proposed expansion of this experiment will generate new opportunities for undergraduate research and additional curriculum development. Students will carry out all of the proposed research to develop genetic markers and plant cultivation methods. A new project will expand the curriculum to include an undergraduate population genetics laboratory, using the long-term experiment as a research framework. The methods developed will contribute to future studies that extend beyond the long-term plots to address questions in evolutionary ecology in natural populations.
The objective of the project was to explore new methods and research approaches for expansion of a long-term ecological experiment in plant community ecology. With initial support from a 2002 NSF Department of Education grant, the long-term experiment was implemented to enrich the ecology curriculum at East Carolina University and provide undergraduate students with authentic research experiences. The cumulative data, collected and analyzed through the years by scores of undergraduate students, reveal that the diversity and composition of a wetland plant community has been significantly impacted by both fertilization and mowing treatments. The current grant focused on the development of genetic and experimental methods to investigate evolutionary processes and population genetic consequences of the treatments, using particular focal species in the plant community. To this end, several candidate species were tested for their utility for future studies. Early efforts involved the development of amplified fragment length polymorphism (AFLP) genetic markers for six common species. For two species – Packera tomentosa and Euthamia caroliniana – the markers were found to be reproducible and highly polymorphic. Large-scale genetic surveys of these two focal species revealed a high degree of genetic variation in each but little evidence for differentiation associated with the treatments. The high degree of genetic polymorphism allowed us to track the spatial extent of clonal growth since the projects’ inception. The data are being analyzed for publication and will serve as a baseline for future surveys. Other work has aimed at developing experimental methods for common garden and reciprocal transplant studies to test for divergence and local adaptation to the treatments. Initial seed germination and greenhouse cultivation trials were successful for several candidate species. Later efforts centered primarily on Euthamia caroliniana. Methods were developed for propagation of replicate clones from rhizomes and field transplant experiments. This species appears to be particularly promising for experimental studies as it is common in the long-term plots, it is readily genotyped using AFLP markers, it reproduces both clonally through rhizomes and sexually, and greenhouse cultivation is rapid and trouble-free. Intriguingly, a preliminary common garden experiment, using plants raised from small rhizome cuttings from the field, revealed significant differences between plants from fertilized and unfertilized plots in their allocation to above- and belowground growth, suggesting potentially important consequences of nutrient addition treatments. As an exploratory grant, the program was successful in supporting pilot studies to initiate several new lines of inquiry, which could be amenable to either undergraduate or graduate student research. Broadly, these focus on ecological and evolutionary mechanisms driving the observed patterns of plant diversity and composition in the plots. Results of a pilot removal experiment in the field plots suggest that increased competition is the mechanism underlying the decline of a species of Solidago in fertilized plots. Future experiments will expand this study and include additional focal species to test the generality of the result. Another undergraduate project underway is exploring the response of rhizomatous growth to nutrient addition. A major new collaboration will ask whether the effects of nutrient and disturbance treatments extend to, or are mediated by, the soil microbial community. Using culture-independent, next generation techniques, microbial communities in the treatment plots will be described, setting the stage for future experimental work on plant-microbe interactions. The project has provided extensive training for graduate and undergraduate students. Four masters students supported by the grant have received training in basic molecular approaches. Of these, two have completed their degrees, one immediately employed in a high level plant genetic breeding position, the other going on to a PhD program in plant evolution. An additional graduate student who worked on propagation techniques is planning a career in rare plant conservation. Seven undergraduates have received molecular training, and some are now in professional schools or biotech positions. Importantly, the long-term ecological experiment provides intensive training in vegetation sampling, plant ID and statistical analysis for a team of 12-15 undergraduates each year, and the plant community data set is used by more than 200 students each year in the ECU general ecology labs. The project has been highlighted in multiple presentations at scientific meetings and has been introduced to the public in annual Earth Day events, including open tours of the long-term plots.
