Eocene Fagaceae from Patagonia and Gondwanan legacy in Asian rainforests.

Abstract

The beech-oak family Fagaceae dominates forests from the northern temperate zone to tropical Asia and Malesia, where it reaches its southern limit. We report early Eocene infructescences of <i>Castanopsis</i>, a diverse and abundant fagaceous genus of Southeast Asia, and co-occurring leaves from the 52-million-year-old Laguna del Hunco flora of southern Argentina. The fossil assemblage notably includes many plant taxa that associate with <i>Castanopsis</i> today. The discovery reveals novel Gondwanan history in Fagaceae and the characteristic tree communities of Southeast Asian lower-montane rainforests. The living diaspora associations persisted through Cenozoic climate change and plate movements as the constituent lineages tracked post-Gondwanan mesic biomes over thousands of kilometers, underscoring their current vulnerability to rapid climate change and habitat loss.