Format: ORAL

Pablo C. Guerrero1,2,3, Sandy Toledo 1,2, Jos A. Garca-Beltrn1,2

1 Departamento de Botánica, Facultad de Ciencias Naturales & Oceanográficas, Universidad de Concepción, Casilla 160C, Concepción, Chile 2 Instituto de Ecología y Biodiversidad, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago 7800024, Chile 3 Millennium Institute Biodiversity of Antarctic and Sub-Antarctic Ecosystems, Santiago 7800003, Chile.

The evolution of the hydrological niche and its contribution to the biogeographical expansion into hyperarid areas enhance our understanding of how lineages adapt to and occupy some of the harshest zones on the planet. This study focuses on a globose and diverse cactus genus, investigating the evolutionary dynamics of the hydrological niche and its associated functional traits. The study encompasses the genus Eriosyce, distributed along a 2,300 km arid gradient on the Pacific coast of southwestern South America. We reconstructed genomic, time-calibrated phylogenies for Eriosyce, analyzing evolutionary shifts in the hydrological niche and functional traits, together with inferences in the historical biogeography related to the occupation of the Atacama Desert. Phylogenetic reconstructions were based on genomic data obtained from whole genome sequencing. Historical biogeography results were compared with independent geological data on the origins of these deserts. We characterized the water sources used by these plants, differentiating between rainfall, groundwater, dew, or fog, by studying water isotopes (2H and 18O). Variations in niche breadth and isotopic signals were found to be related to the microhabitats occupied and the growth forms of the species. Significant lag times were observed between the colonization of the region and the invasion of hyperarid habitats by Eriosyce subclades, with an inferred historical biogeographical route from less arid habitats, such as Mediterranean central Chile, to the hyperarid desert. The findings suggest that adaptation to extreme environments like deserts, which have been evolving for millions of years, is a slow and complex process. This presents significant challenges for the survival of various species in the face of rapid climate change.