On the tectonic and climatic controls to the evolutionary patterns of Andean plant groups

Life, climate, and landforms interact to shape the biodiversity patterns we observe in Earth’s Mountain regions. Plausible tectonic and climatic explanations have emerged to explain, for example, the evolutionary patterns of Andean plant groups. However, it remains unclear how different tectonic and climatic histories affect the evolution of Andean flora on geological time scales. Here we present the results of numerical experiments using our coupled speciation and landscape evolution model to investigate how tectonics and climate interact to produce distinct evolutionary histories in the Andes. To address this, we first calibrated our model using a Bayesian inversion algorithm with observations of present-day topography and precipitation, paleo-elevation reconstructions, and thermochronological data to calibrate three scenarios with different uplift histories, which were designed based on the literature and named as propagating and compound. The propagating scenario considers the west-to-east propagation of a Gaussian-shaped wave of uplift, which has been shown to adequately approximate the evolution of plateaus. The compound scenario divides the landscape into 6 geomorphic regions, each with its uplift history. Additionally, we tested a third scenario as a control, in which we maintained the present-day topography for the course of the simulation (ca. 80 Myr), which we named static. We ran the eco-evolutionary component of our model in these three distinct uplift scenarios, covering the mountain building of the Andes for the past 80 Myrs, and designed a series of ensemble simulations in which we randomly assigned dispersal and mutation variability to recreate different assemblages with distinct evolutionary histories and evaluate if the different scenarios produce any consistent speciation patterns comparable to reported time-calibrated phylogenies of various plant groups. We found that the uplift scenario with a more complex uplift history, i.e. compound, better agrees with the different observations. This scenario also showed increased diversification during the Miocene (23-4.5 Ma), a feature observed in several Andean plant groups. This demonstrates how diversification constraints obtained from phylogenetic studies can be used to discriminate between conflicting uplift scenarios for the Andes/Altiplano that have been suggested by paleo-altimetry estimates and other geological observations.