Local geographic variation in the secondary metabolites of Usnea strigosa

Ayla Edmiston

Although the most common secondary chemicals of the lichen species Usnea strigosa have been identified in different regions throughout the range of the taxon, and chemotypes have been named, smaller differences in secondary chemistry have not been described. In this study, we examined local geographic variation in the suite of secondary chemicals produced by U. strigosa by identifying and comparing the secondary metabolites of samples collected from 11 sites across Greenwood, South Carolina. Potential secondary metabolites of U. strigosa were identified using thin-layer chromatography (TLC). Solvent system C, which contains toluene and acetic acid (170:30) was used to provide an initial analysis of the data as well as to identify the secondary metabolites common in local lichen samples. We predicted that the chemical variation we detected in the suite of chemicals produced by U. strigosa would be better explained by local geographic differences than by individual variation among lichen samples. Although individual lichen samples showed small differences in their secondary chemistry, we found significant local variation between collection sites (ANOSIM, p = .001) and visualized these differences using non-metric multidimensional scaling (NMDS) plots. Further research in this system will include identifying the specific secondary chemicals that are ubiquitous in U. strigosa and those that are responsible for the local variation we observed.

• Ayla Edmiston is junior biology major with minors in chemistry, forensic science, and psychology. She is a member of TriBeta Biological Honors Society and the Honors College. She is expected to graduate in May 2023.