Investigation of temporal variation in secondary metabolites of Usnea strigosa

Jordan Cannon

The basic chemical composition of common lichens is often well known because it is required for the successful identification of lichen taxa; however, the ecological roles of the secondary metabolites produced by lichens are just starting to be investigated. In this study, we examined temporal variation in secondary chemistry for a lichen common to our region, Usnea strigosa. Between August and November, we collected 10 U. strigosa samples each week from downed limbs in a single population, and we used thin-layer chromatography to identify potential secondary compounds. In order to quantify changes in chemistry over time, we used ANOSIM which allowed us to detect differences between collection weeks. We then visualized our data using NMDS. We found what initially appeared to be temporal differences in secondary chemistry (p = .001). However, upon inspection of our NMDS plots, we found that the four groups identified in our ordination did not only differ temporally but also spatially (at the level of substrate or microscale). After removing the weeks in which samples were collected from different substrates (trees), we analyzed the remaining data (approximately 9 weeks of samples). In the subsequent NMDS plot, the samples were all part of the same group showing no obvious temporal variation in secondary chemistry. Upcoming research will include a description of substrate-level differences in chemistry and collection of additional lichen samples from the collection area that did not appear to show temporal variation.

• Jordan Cannon is a biology major with psychology and chemistry minors, expecting to graduate in May of 2023. She is a member of Lander University’s Honors College and is preparing to apply to graduate school for genetic counseling in the fall of 2022.