Biology subjects

Hernandez-Hernandez, T.

Publications and source records attributed to Hernandez-Hernandez, T..

3 recordsLinked to original sources

bioRxiv2023

Did succulents diversify in response to aridity? Evolutionary analyses of major succulent lineages around the world

The succulent syndrome is one of the most iconic life strategies in angiosperms, maximising water storage through a suite of adaptations to water-scarcity. 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. Here we analyse time-calibrated phylogenetic reconstructions of the seven richest lineages of succulents, and study diversification dynamics in relation to abiotic variables. Our analyses reveal different levels of 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 suggest these phenomena are decoupled, indicating that succulence might not adhere to a classic key innovation model. We discuss that these evolutionary patterns reveal the ecological complexity of the succulent strategy, beyond simplistic interpretations as adaptations towards aridity.

plant biology↗

bioRxiv2023

Climatic niches provide insights into the evolutionary origins and ecological significance of the succulent CAM syndrome around the world

Although distributed globally, plants possessing the succulent syndrome are thought to have evolved to adapt to arid climates, because they possess modifications that increase their water use efficiency. Here we study the evolution and the ecological nature of the succulent CAM syndrome at a global scale by analyzing the climatic niches of succulents within the Caryophyllales, testing the hypothesis of a climatic niche specialization by comparing them with their non-succulent, non-arid adapted relatives. We assembled and carefully curated a worldwide dataset of 5447 species in 28 families, and analyzed the current and evolutionary trajectories of climatic niches with an array of statistical methods including ecological niche modeling, phylogenetic regression and divergence dates estimation. Our results confirm the Core Caryophyllales tend to inhabit drylands probably since their origin in the Early Cretaceous. However, the succulent syndrome appeared later with some lineages diversifying profusely afterwards. The climatic niche of succulents is 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 support alternative interpretations of the origin of the CAM syndrome and the ecological significance of succulence, as well as the prolific radiation of richest lineages. HighlightsThe climatic niche occupied by succulent CAM plants is not different from their non-succulent relatives. Estimated dates and character reconstruction suggest CO2 scarcity as the evolutionary pressure under these plants originated.

plant biology↗

bioRxiv2023

Identifying the multiple drivers of Cactus diversification

Many drivers of diversification have been identified across the angiosperm Tree of Life, ranging from abiotic factors, such as climate change, to biotic factors such as key adaptations. While this provides invaluable evolutionary insight into the rise of major angiosperm lineages, our understanding of the complexity underlying this remains incomplete. In species-rich families such as Cactaceae, simple explanations of triggers of diversification are insufficient. Their sheer morphological and ecological diversity, and wide distribution across heterogeneous environments, render the identification of key forces difficult. Cactus diversification is likely shaped by multiple drivers, which themselves interact in complex ways. This complexity is extremely difficult to disentangle, but applying modern analytical methods to extensive datasets offers a solution. Here, we investigate the heterogeneous diversification of the iconic Cactus family. We reconstruct a comprehensive phylogeny, build a dataset of 39 abiotic and biotic variables, and predict the variables of central importance to tip-speciation rate variation using Machine Learning. State-dependent diversification models confirm that a rich range of eleven abiotic and biotic variables filtered as important by Machine Learning shape Cactus diversification. Of highest importance is an atypical latitudinal gradient in speciation rates, which is spatially decoupled from richness hotspots. Of medium importance is plant size, shaped by growth form. Of lesser, but significant, importance is soil composition, bioclimate, topography, geographic range size, and chromosome count. However, it is unlikely that any one of these eleven variables is of primary importance without the complex interactions formed with others. Our results contribute to our understanding of one of the most iconic angiosperm families, while revealing the need to account for the complexity underlying macroevolution.

evolutionary biology↗