Format: ORAL

Cibele Cssia-Silva1 Christine D. Bacon2 Rafael S. Oliveira1

1 Department of Plant Biology, University of Campinas, Campinas, Brazil 2 Department of Biological and Environmental Sciences, University of Gothenburg,Göteborg, Sweden

Palms (Arecaceae) likely originated in TRF-like ecosystems of Laurasia in the mid-Cretaceous. While many palm lineages fail to colonize seasonally dry habitats, the evolution of drought-avoidance traits enables certain clades, like the tribe Cocoseae, to thrive. The acaulescence growth form, linked to outstanding cocosoid palm diversification in Latin America, involves an underground stem, enhancing survival during seasonal dry spells and fires. Acaulescence serves as a preadaptation allowing rainforest cocosoid lineages to colonize new fire-prone and drier zones. Indeed, geographic distribution patterns of palms seem closely tied to their traits, particularly in both seasonally dry habitats and islands. Insular habitats play a crucial role in shaping palm trait diversity, with island palms exhibiting higher evolutionary rates for height, fruit size, and predominantly being dioecious. Trait flexibility in sexual system evolution and the in situ radiation of dioecious lineages contribute to the outstanding distribution of palms on islands. As sessile organisms, plants respond to environmental change through reproductive traits. Spatial segregation and physiological specialization of sexes in dioicous plants create mismatches in individual responses to environmental change. Conversely, self-fertilization, linked to the dominance of hermaphrodites in drought-stressed habitats, circumvents the need for sexual partners. Different sexual systems of palms (dioecy, hermaphroditism, monoecy, and polygamy) respond similarly to climate change, with reductions in potential distribution expected for all systems. Climate change threats to global palm richness are ubiquitous but uneven geographically. Most species are expected to lose suitable areas, particularly in Latin America, where palm richness is concentrated. Sharp richness loss is projected for Amazonia and Cerrado, the sources of diversification of drought-avoidance traits like acaulescence. Our studies underscore the intricate interplay between evolutionary history, functional traits, and environmental change in shaping the fate of palm diversity.