Warming and precipitation change alter flowering phenology in California serpentine grasslands

This project examines how climate change alters the timing of flowering among California serpentine grassland annuals and, in turn, the networks they form with pollinators. When many species flower together, these “coflowering networks” draw more pollinators but also increase the risk of pollen mixing between species, while weaker networks reduce both pollination and pollen contamination. By building experimental communities of up to 12 serpentine annual species and exposing them to different rainfall and temperature conditions, I tracked weekly flowering patterns over a growing season. Early findings show that warming reduces overlap among late-season flowers, that plants at different times of year respond differently to soil moisture under heat, and that species with different traits also respond in distinct ways. These changes threaten to disrupt pollinator foraging, especially in the late dry season, putting at risk both pollinators and the rich diversity of these unique grasslands.