Format: ORAL

Jamie B Thompson1, Marilyn Vsquez-Cruz2, Israel Loera3, Melina DelAngel4, Miguel Nakamura4, Kevin R Hultine5, Santiago Ramrez-Barahona6, Nicholas K Priest1, Tania Hernndez-Hernndez5

1 The Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, UK 2 Tecnológico Nacional de México/ITS Irapuato, Gto, México 3 Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA 4 CIMAT (Centro de Investigación en Matemáticas A.C.), Guanajuato, Gto, México 5 Department of Research, Conservation and Collections, Desert Botanical Garden, Phoenix, AZ, USA 6 Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad de México, México

Succulents have been typically considered the iconic example of arid adapted plants. Although distributed globally, plants possessing the succulent syndrome are assumed to have evolved to adapt to arid climates, because they possess modifications that increase their water use efficiency. Though succulence is considered a classic case of convergent evolution driven by shared environmental drivers, we lack a full understanding of whether the timing and drivers of the diversification of succulent lineages are, in fact, concordant; or even whether their climatic niches are indeed trending towards arid climatic conditions. We present our recent findings about the timing; climatic niches and evolutionary dynamics of major succulent lineages globally. Our analyses reveal different levels of evolutionary synchronicity and relation with aridity. The impact of atmospheric CO2 on succulent macroevolution is varied. While transitions and radiations are especially concentrated in recent time, following a collapse of atmospheric CO2 ~15 million years ago, CO2-dependent diversification is not supported in most lineages. With the exception of Euphorbia, we find that succulence elevates net diversification, though the effects on underlying speciation and extinction disagree. The phylogenetic distribution of transitions to succulence and rate shift increases suggests these phenomena are decoupled, indicating that succulence might not adhere to a classic key innovation model. The climatic niches of succulents are not differentiated from their non-succulent relatives, but narrower, and contained within the non-succulents’, showing no relationship with extreme conditions such as high aridity or temperatures. Our results reveal the complexity of the succulent strategy, as well as the abiotic conditions and ecological contexts under which the different succulent lineages evolved.