DOI: 10.5061/dryad.1c59zw3wd
title: Data from: Rapid, parallel evolution of field mustard (Brassica rapa) under experimental drought

description: Climate change is driving evolutionary and plastic responses in
 populations, but predicting these responses remains challenging. Studies
 that combine experimental evolution with ancestor-descendant comparisons
 allow assessment of the causes, parallelism, and adaptive nature of
 evolutionary responses, although such studies remain rare, particularly in
 a climate change context. Here, we created experimental populations of
 Brassica rapa derived from the same natural population and exposed these
 replicated populations to experimental drought or watered conditions for
 four generations. We then grew ancestors and descendants concurrently,
 following the resurrection approach. Experimental populations under
 drought showed rapid evolution of earlier flowering time and increased
 specific leaf area, consistent with a drought escape strategy and
 observations in natural populations. Evolutionary shifts followed the
 direction of selection and increased fitness under drought, indicative of
 adaptive evolution. Evolution to drought also occurred largely in parallel
 among replicate populations. Further, traits showed phenotypic plasticity
 to drought, but the direction and effect size of plasticity varied. Our
 results demonstrate parallel evolution to experimental drought, suggesting
 that evolution to strong, consistent selection may be predictable.
 Broadly, our study demonstrates the utility of combining experimental
 evolution with the resurrection approach to investigate responses to
 climate change.
description: We combined experimental evolution with the resurrection approach
 to explore adaptation to experimental drought in Brassica rapa (field
 mustard).  We founded 24 experimental populations from
 lines which originated from a natural population and randomly assigned
 each experimental population to a watering regime. We assigned 8
 populations for storage as ancestors, 8 to receive four generations of
 experimental drought, and 8 to receive four generations of experimental
 well-watered conditions. During these four generations of experimental
 evolution, drought regime populations received a draw-drown drought
 treatment aimed to mimic Mediterranean drought while well-watered regime
 populations were watered every other day. We collected data (flowering
 time, survival, and seed mass) on a subset of individuals each generation
 to explore trends in fitness and selection during experimental evolution.
   After experimental evolution, we grew all
 experimental populations (ancestors included) under unstressed
 (well-watered) conditions to reduce maternal and storage condition effects
 across the different regimes.  We then grew two seeds
 (siblings) from 35 individuals per population while applying a watering
 treatment with one sibling from each individual under each treatment in
 what was the test generation. This design allowed us to assess
 evolutionary responses (ancestor-descendant regime comparisons),
 plasticity (watered-drought treatment comparisons), and consistency of
 responses (parallelism among replicates) to experimental
 drought. Detailed methods, statistical analysis, and
 results are discussed in the associated manuscript published in
 Evolution.
description: # README file for Johnson et al. 2022 manuscript published in Evolution ##
 Manuscript link & citation: Johnson, S. E., Hamann, E., & Franks,
 S. J. (2022). Rapid, parallel evolution of field mustard (Brassica rapa)
 under experimental drought, Evolution 76(2), 262–274.
 ## Dryad repository link:
 ##
 Data files: For each file, the data is found in the first tab while an
 explanation of each variable is provided in the second tab. The file named
 "Johnson_et_al_2022_Evolution_individuals_data.xls" includes
 traits measured for all individuals during the test generation of the
 experiment (flowering time, stem diameter, specific leaf area, and seed
 mass). The file named
 "Johnson_et_al_2022_Evolution_WUE_data.xls" contains data for
 water-use efficiency, which is a trait that was measured on population
 pools, during the test generation of the experiment. The file named
 "Johnson_et_al_2022_Evolution_EE_subset.xls" contains flowering
 time and seed mass information for 40 individuals per watering regime
 (drought or watered) for each generation (1-4) during experimental
 evolution. This was used to estimate survival and selection during the
 experiment. ## Code files: The file named
 "Johnson_et_al_2022_Evolution_code.txt" contains all code used
 to generate results included in the Evolution journal article. This code
 is explained with comments throughout the text file.