Data from: Insights on the evolution of plant succulence from a remarkable radiation in Madagascar (Euphorbia)

Patterns of adaptation in response to environmental variation are central to our understanding of biodiversity, but predictions of how and when broad-scale environmental conditions such as climate affect organismal form and function remain incomplete. Succulent plants have evolved in response to arid conditions repeatedly, with various plant organs such as leaves, stems, and roots physically modified to increase water storage. Here we investigate the role played by climate conditions in shaping the evolution of succulent forms in a plant clade endemic to Madagascar and the surrounding islands, part of the hyper-diverse genus Euphorbia (Euphorbiaceae). We used multivariate ordination of 19 climate variables to identify links between particular climate variables and three major forms of succulence – succulent leaves, cactiform stem succulence, and tubers. We then tested the relationship between climatic conditions and succulence, using comparative methods that account for shared evolutionary history. We confirm that plant water storage is associated with the two components of aridity, temperature and precipitation. Cactiform stem succulence, however, is not prevalent in the driest environments, countering the widely held view of cactiforms as desert icons. Instead, leaf succulence and tubers are significantly associated with the lowest levels of precipitation. Our findings provide a clear link between broad-scale climatic conditions and adaptation in land plants, and new insights into the climatic conditions favoring different forms of succulence. This evidence for adaptation to climate raises concern over the evolutionary future of succulent plants as they, along with other organisms, face anthropogenic climate change. Molecular sequence data for Euphorbia sections Goniostema, Denisophorbia, and Deuterocalli.Aligned sequence data for ITS, ETS, atpI-atpH, psbA-trnH, matK, ndhA, trnQ-rps16, and rbcL for 279 samples in Euphorbia sections Goniostema, Denisophorbia, and Deuterocalli (ingroup) and appropriate outgroup samples in the genus Euphorbia.Molecular_data_Evansetal.nexFigure S1. Maximum clade credibility tree obtained from a BEAST analysis of the combined Euphorbia GDD dataset, showing the distribution of the 67 samples selected for trait analyses, from a total of 279 samples.Maximum clade credibility tree obtained from a BEAST analysis of the combined Euphorbia GDD dataset, showing the distribution of the 67 samples selected for trait analyses, from a total of 279 samples. Black branches indicate parts of the larger phylogeny captured by our subsample (i.e., taxa for which multiple samples were available and whose monophyly was confirmed). Stars indicate the location of those 67 samples. Grey branches indicate parts of the larger phylogeny not captured by this subsample. The seven subclades emphasized in the text are labeled.FigureS1.pdfFigure S2. (a) Ordination diagram (b) and eigenvectors illustrating the loading of 19 Bioclim variables in PCA axis 1 vs. axis 2 space.PCA ordination of bioclim data extracted for 67 taxa in Euphorbia sections Goniostema, Denisophorbia, and Deuterocalli.FigureS2.pdfFigure S3. (Lower panels) Evolution of the cactiform growth form mapped on the trimmed maximum clade credibility tree optimized in climate space, and (upper panels) predicted probability of the cactiform growth form, as a function of the same climate gradient.Figure S3. (Lower panels) Evolution of the cactiform growth form mapped on the trimmed maximum clade credibility tree optimized in climate space, and (upper panels) predicted probability of the cactiform growth form, as a function of the same climate gradient. a) Lower panel: stochastic character mapping of the cactiform growth form on the phylogeny optimized with respect to mean annual temperature (MAT). Upper panel: predicted probability of the cactiform growth form, as a function of MAT. b) As in a, but the x-axis is mean annual precipitation (MAP). The upper panel shows the predictions from three models: MAP as a linear term only, MAP as linear and quadratic terms, and the latter model after removing two outliers, E. lophogona and E. boissieri. c) Stochastic character mapping of the cactiform growth form on the same tree. This character reconstruction matches panel b, whereas an alternative possible history of the evolution of the cactiform growth form is shown in panel a.FigureS3.pdfGenbank numbers and voucher information for samples used in this study.Genbank numbers and voucher information for samples used in this study.Supplementary_Table_1.xls