Understanding the evolution of secondary chemistry in lichens

2010 REU Intern Jessica Allen


Junior Biology major at Eastern Washington University

REU Mentor: Dr. Thorsten Lumbsch (Curator, Botany)

Symposium Presentation Title: Species delimitation in melanelioid lichens

Symposium Presentation Abstract: Recent estimates of the number of fungal species worldwide range from 700K to 1.5 M. However, only about 100K fungal species have been described thus far, which is partially due to species circumscription not reflecting natural relationships. Molecular data have shown that traditional morphology-based species delimitation generally underestimates the number of actual taxa. This is partially due to traditional species circumscription working under the assumption that the “everything is everywhere” hypothesis applies to lichenized fungi, so biogeographical patterns were largely ignored. However, recent studies have shown that geographically isolated populations of lichens are in fact distinct lineages. In this study we focus on species circumscription in melanelioid lichens, a group within the large family Parmeliaceae, and specifically investigate whether populations on different continents are separate species.  Fifty-four new nuclear ITS rDNA sequences were generated, and these sequences were combined with 55 others downloaded from GenBank to form our complete dataset. Maximum likelihood analysis revealed that members of some currently circumscribed species from different continents appear to form distinct lineages. These findings are promising and further studies using multiple loci, extended sampling and a variety of analyses will allow confident delimitation of the species in this group of lichens as well as aid in developing empirical methods to test species boundaries in other lichenized fungi.

Original Project Description: Secondary metabolites are common among fungi, including important antibiotics, such as penicillin. Fungi that produce phenolic secondary metabolites are either lichen-forming or derived from lichen ancestors. Recently, we have demonstrated that the genes responsible for the production of phenolics are very similar to those found in soil bacteria and hypothesized that they were probably gained by the lichen fungi by horizontal gene transfer from these bacteria. This project would focus on the occurrence of secondary metabolites in one of the largest families of lichen-forming fungi, the Lecanoraceae. Secondary metabolites traditionally play a major role in the taxonomy of lichen-forming ascomycetes. In this specific project, phylogenies inferred from genetic markers will be used to reconstruct the evolution of the chemical profile of Lecanoraceae and to evaluate the taxonomic importance of this character in this family.

Research methods and techniques: REU participants in this project will receive training in molecular and organismal research methods. They will learn how important a combination of both methods is for an understanding of the evolution of the diversity of life. The training will include introduction to the literature, handling of herbarium specimens. Chemical examination will include chromatographic methods, such as HPTLC and HPLC. Molecular methods will include DNA isolation, PCR and subsequent direct sequencing of certain gene regions. Subsequently, the analysis of DNA sequence data will be performed.