Under the guidance of faculty adviser Dr. William Culberson, graduate student Paula DePriest will study genetic variation and species boundaries in lichens using new molecular-biological methods. Lichens, fungal and algal partners forming long-lived and durable associations, are the best-known examples of symbiosis. As one feature of this symbiosis, the fungal partner makes unique chemical substances, lichen secondary products, which may protect the lichen against herbivory. These secondary compounds have been used for over a hundred years as characters to identify lichen species, and when correlated with geographic distribution or ecology, they have also been used to define a lichen species. In this study the student will examine the relationship between four chemotypes that cannot be recognized from their morphology alone--they have different secondary products but all look alike. These chemotypes occur in mixed populations in the southern Appalachians. Do they represent separate, reproductively isolated species or are they variable parts of one species? The immediately obvious experimental approaches will not work; for example, crossing individuals of different chemotypes in the field is technically impossible and lichen cultures in the laboratory do not reproduce sexually. In this study, newly developed DNA technologies for analyzing variants of ribosomal gene sequences will be employed to measure genetic relatedness among the chemotypes and their sporelings in the laboratory. Genetic similarity between different chemotypes, based on the sharing of molecular-genetic markers, will indicate that they are members of a single species. Differences in molecular-genetic markers will indicate reproductive isolation and separate species status. These new techniques will allow routine genetic evaluation of lichen relatedness and provide new tools for the taxonomic investigation of lichens.
