Morphological Diversity, Distribution, and Reproductive Mode of Epiphytic Lichens on Baccharis pilularis
Katrina McCollough
Department of Biology
Faculty Supervisor: Jenna Ekwealor
San Bruno Mountain, spanning four square miles of preserved habitat in the San Francisco Peninsula, serves as an ecological island within an urban landscape. It offers a unique setting to study environmental gradients, including marine influences such as coastal fog and oceanic proximity, and their effects on native organisms. Lichens, symbiotic organisms composed of fungi and photosynthetic partners, are well-suited for studying non-rainfall water inputs, as they can uptake fog and dew directly for hydration and metabolism. This research investigates how elevation and moisture availability influence lichen morphological diversity, distribution, and reproductive mode on Baccharis pilularis, a dominant chaparral shrub. We conducted a species composition survey along a coastal-inland transect, identifying 13 genera and 693 individual lichens. Inland specimens exhibited significantly larger lobes, and asexual reproduction was more prevalent, particularly in the fruticose genera Ramalina, Usnea, and Teloschistes. We will use PCR-amplification of targeted markers and Sanger sequencing to confirm identification, complementing morphology-based determinations. Going forward, we aim to expand the dataset by incorporating crustose species and refining environmental data collection through weather stations. By advancing our understanding of lichen ecology, this study supports conservation as it emphases lichens’ role in the water cycle and ecosystem stability in California’s chaparral.