Format: ORAL

Mwihaki J. Karichu1,2,3*, Boniface K. Ngarega4, Jefwa JM5, Bette A. Loiselle6, Emily B.Sessa2

1. The Lewis B. and Dorothy Cullman Program for Molecular Systematics, New York Botanical Garden, 2900 Southern Blvd, Bronx, NY 10458. 2. New York Botanical Garden, 2900 Southern Blvd, Bronx, NY 10458. 3. Graduate Center, City University of New York, 365 5th Ave, New York, NY 10016, USA. 4. Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, Stillwater, OK 74078-3013, USA. 5. Pwani University, P.O Box 195, 80108, Kilifi, Kenya. 6. Department of Wildlife Ecology and Conservation and Center for Latin American Studies, University of Florida

Tropical forests in Africa are rapidly declining due to increasing population, recurrent wildfires, logging, land use changes, agricultural intensification, and other socioeconomic factors. This study utilized maximum entropy modeling, paleoclimatic data, and future climate scenarios to evaluate the historical presence of tree ferns in tropical and Saharan Africa during the African Humid Period (AHP; ca. 14,500-5,000 years ago) and project the impacts of climate change on their future distribution and implications for African forests. Although precipitation increased substantially during the AHP, the distribution was variable and insufficient to support all tropical plant species. We found most African tree fern species persisted in refuge areas that survived the late Pleistocene extinction. These refugia provided a haven for tree ferns, enabling them to survive despite challenging and fluctuating conditions. This highlights the remarkable resilience and adaptability of tree ferns and the critical importance of refugial areas in safeguarding populations during climatic upheaval. Our study further shows tree fern species had differential responses to climate change, with some experiencing minimal range contractions of 5.9% up to over 57% range expansion. Preserving these refugia not only protects tree ferns but also conserves overall forest biodiversity and ecosystem functioning. This knowledge is vital for targeted conservation to promote sustainable forest management and mitigate threats from climate change and human activities in African closed wet forests. Key Words: Africa; African Humid Period; Alsophila; Ferns; MaxEnt; Tree Ferns; Tropical Forests