DOI: 10.5061/dryad.7wm37pw3s
title: Data from: Drought tolerance as an evolutionary precursor to frost and winter tolerance in grasses

description: Accumulating evidence is suggesting more frequent tropical-to-temperate
 transitions than previously thought. This raises the possibility that
 biome transitions could be facilitated by precursor traits. A wealth of
 ecological, genetic and physiological evidence suggests overlap between
 drought and frost stress responses, but the origin of this overlap, i.e.
 the evolution of these responses relative to each other, is poorly known.
 Here, we test whether adaptation to frost and/or severe winters in grasses
 (Poaceae) was facilitated by ancestral adaptation to drought. We used
 occurrence patterns across Köppen-Geiger climate zones to classify species
 as drought, frost and/or winter tolerant, followed by comparative
 analyses. Ancestral state reconstructions revealed different evolutionary
 trajectories in different clades, suggesting both drought-first and
 frost-first scenarios. Explicit simultaneous modelling of drought and
 frost/winter tolerance provided some support for correlated evolution, but
 suggested higher rates of gain of frost/winter tolerance in drought
 sensitive rather than drought tolerant lineages. Overall, there is limited
 support across grasses as a whole that drought tolerance acted as an
 evolutionary precursor to frost or severe winter tolerance. Different
 scenarios in different clades is consistent with present-day grasses being
 either cold or drought specialists, possibly as a consequence of
 trade-offs between different stress tolerance responses.
description: # Data from: Drought tolerance as an evolutionary precursor to frost and
 winter tolerance in grasses
 [https://doi.org/10.5061/dryad.7wm37pw3s](https://doi.org/10.5061/dryad.7wm37pw3s) ## Description of the data and file structure This data accompanies the following article:  Schat, L., M. Schubert, S. Fjellheim, and A. M. Humphreys. 2024. Drought tolerance as an evolutionary precursor to frost and winter tolerance in grasses.* Evolution* The data includes: 1. A csv file with the scoring for drought, frost and sever winter for the 2800 species included in the study. The three tolerances have been scored under three thresholds: if at least 20% of their geographical observations fell in Köppen-Geiger zones scored accordingly (this is the main dataset; drought20, frost20, winter20), 5% (drought5, frost5, winter5) and 50% (drought50, frost50, winter50). 1 indicates tolerance and 0 indicates sensitivity. 2. A csv file with 500 simulated binary traits that has evolved independently of either frost or winter tolerance. These traits were simulated using the “sim.Mk” function in the R package "phytools" (Revell, 2012) and the transition rate matrix inferred from the best fitting Markov model for drought tolerance (three-rate model; 20% dataset). 1 indicates tolerance and 0 indicates sensitivity.' 3. A csv file with the results of corHMM models with transition rate category for frost tolerance (20% threshold) and each of the 500 simulated traits (Beaulieu et al., 2013). The file includes the LogL and AICcs of the independent and correlated models, and the delta AICc used to compare these models.  4. A csv file with the results of corHMM models with transition rate category for frost tolerance (20% threshold) and each of the 500 simulated traits (Beaulieu et al., 2013). The file includes the LogL and AICcs of the independent and correlated models, and the delta AICc used to compare these models.  Beaulieu, J. M., B. C. O’Meara, and M. J. Donoghue. 2013. Identifying Hidden Rate Changes in the Evolution of a Binary Morphological Character: The Evolution of Plant Habit in Campanulid Angiosperms. Syst. Biol. 62:725–737. Oxford Academic. Revell, L. J. 2012. phytools: an R package for phylogenetic comparative biology (and other things). Methods Ecol. Evol. 3:217–223. ### Files and variables #### File: Schatetal2025\_DroughtFrostWinterData.csv **Description:**  ##### Variables * species: name of the species * drought20: drought scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * frost20: frost scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * winter20: severe winter scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * drought5: drought scored using the 5% threshold; 1 indicates tolerance and 0 indicates sensitivity * frost5: frost scored using the 5% threshold; 1 indicates tolerance and 0 indicates sensitivity * winter5: severe winter scored using the 5% threshold; 1 indicates tolerance and 0 indicates sensitivity * drought50: drought scored using the 5% threshold; 1 indicates tolerance and 0 indicates sensitivity * frost50: frost scored using the 5% threshold; 1 indicates tolerance and 0 indicates sensitivity * winter50: severe winter scored using the 50% threshold; 1 indicates tolerance and 0 indicates sensitivity #### File: Schatetal2025\_FrostSimulationsCorHMMResults.csv **Description:**  ##### Variables * simulation: number of the simulation * logL_independent: logL value of the independent model * AICc_independent: AICc value of the independent model * logL_correlated: logL value of the correlated model * AICc_correlated: AICc value of the correlated model * delta_AICc: delta AICc value #### File: Schatetal2025\_WinterSimulationsCorHMMResults.csv **Description:**  ##### Variables * simulation: number of the simulation * logL_independent: logL value of the independent model * AICc_independent: AICc value of the independent model * logL_correlated: logL value of the correlated model * AICc_correlated: AICc value of the correlated model * delta_AICc: delta AICc value #### File: Schatetal2025\_TraitSimulations.csv **Description:**  ##### Variables * species: name of the species * drought: drought scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * frost: frost scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * winter: severe winter scored using the 20% threshold (main dataset); 1 indicates tolerance and 0 indicates sensitivity * SimulationX: values of each simulated trait; 1 indicates tolerance and 0 indicates sensitivity