Leaf traits and seasonal effects on foliar fungal endophyte diversity in Asclepias fascicularis

Foliar fungal endophytes (FFE) are highly diverse and present in nearly all terrestrial plants. FFE play important roles in host plant ecological dynamics, including enhancing tolerance to both abiotic and biotic stresses. Despite this, FFE are not fully understood, especially in their associations with leaf traits and seasonality. This study examines leaf traits and FFE diversity in Californian A. fascicularis populations using a Santa Barbara common garden. Leaves were collected from the same 20 plants in April and July 2025. Culturable FFE were identified using Sanger sequencing of the ITS region. We hypothesize that increasing leaf area allows more FFE colonization opportunities and thus increases diversity. Drier months are associated with reduced stomatal opening, potentially limiting opportunities for FFE colonization and reducing diversity. Insights provided from this project can enhance restoration efforts for milkweeds and further support endangered monarch butterflies.