Rapid, parallel evolution of field mustard (Brassica rapa) under experimental drought

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 ev..., 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 unst..., , # 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...