DISSERTATION RESEARCH: Do environmental constraints on photosynthetic symbionts alter the community structure of their fungal partners? A case study with canopy lichens.

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Most organisms, including humans, live in close association with other species. When such partnerships are obligatory, the ability of one species to tolerate a particular environment may limit where its partner species can live. Lichens are thought to provide a good example of this type of constraint. All lichens consist of two, mutually-dependent organisms: a fungus and an alga. Lichens have adapted to some of Earth's harshest environments and play an important role in several ecosystems. Despite lichens' ubiquity, relatively little is known about the diversity of their algae and whether the environmental tolerances of those algae constrain where lichens can grow. The goal of this project is to determine how light availability impacts the health and distribution of algae and lichens. Understanding how communities of mutually-dependent species shift along environmental gradients is a necessary precursor to predicting how these interactions will respond to global environmental change. This research will provide interdisciplinary training in molecular biology to a graduate student studying ecology. Such training facilitates cross-disciplinary communication and will enable a broader variety of future collaborations. The project also supports an undergraduate student to conduct independent research in canopy ecology. Participating in an independent research project develops a student's critical thinking and communication skills and builds self-confidence. Special effort will be made to recruit a student from a demographic under-represented in the sciences. In addition, the researchers are involved in an ongoing partnership with the North Carolina School of Science and Math to develop educational units that use lichens to teach key concepts in biology.More specifically, the goal of this project is to determine whether environmental gradients in forests impose differential constraints on fungal and algal partners, with cascading effects on lichen diversity. Molecular community profiling methods will be used to relate community composition of lichen-forming fungi and algae to light and temperature gradients in tree canopies in North Carolina. By concurrently measuring fungal and algal diversity, the researchers can test whether light constraints on algae subsequently limit their fungal partners. Results will be used to construct a general model of stochastic community assembly of mutualist populations. This model can then be applied more generally to interpret how environment changes will constrain or facilitate the structure and occurrence of other mutualistic networks.