Coastal fog and butterflies: How does microclimate impact butterfly habitat in San Francisco

Abstract

In this thesis we explore the relationships between coastal fog, the Coastal Green Hairstreak butterfly (Callophrys viridis) and the Seaside daisy plant (Erigeron glaucus). We address three broad questions: 1) How has the Green Hairstreak’s habitat in San Francisco changed over time? 2) How do Green Hairstreak butterflies interact with Seaside daisy plants within their restored habitats? and 3) How does coastal fog influence the physiological function of Seaside daisy plants? Our results strongly suggest that coastal fog has a lasting impact on habitat quality. Our historical analysis shows that the Green Hairstreak butterflies are restricted to foggy coastal areas and that urbanization has negatively impacted their habitat. We observed that plant-butterfly interactions were influenced by microclimate conditions and plant characteristics, such as floral display and flower size. At the plant scale, we found that coastal fog enhances the physiological function of Seaside daisies (i.e., namely photosynthesis rates and stomatal conductance), which can help to alleviate drought stress. Finally, we use this information provide restoration recommendations which aim to improve habitat quality within the Green Hairstreak Corridor.