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

Citation

Johnson, Stephen; Hamann, Elena; Franks, Steven (2021), Data from: Rapid, parallel evolution of field mustard (Brassica rapa) under experimental drought, Dryad, Dataset, https://doi.org/10.5061/dryad.1c59zw3wd

Abstract

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.

Methods

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 fitnesss 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 replcates) to experimental drought.
Detailed methods, statistical analysis, and results are discussed in the assocated manuscript published in Evolution.

Usage Notes

Johnson_et_al_2021_Evolution_individuals_data.xls

This file includes traits measured for all individuals during the test generation of the experiment (flowering time, stem diameter, specific leaf area, and seed mass). Data is found in the first tab of the file while an explanation of each variable is provided in the second tab.

Johnson_et_al_2021_Evolution_WUE_data.xls

This file contains data for water-use efficiency, which is a trait that was measured on population pools, during the test generation of the experiment. Data is found in the first tab of the file while an explanation of each variable is provided in the second tab.

Johnson_et_al_2021_Evolution_EE_subset.xls

This file 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. Data is found in the first tab of the file while an explanation of each variable is provided in the second tab.

Johnson_et_al_2021_Evolution_manuscript_code.txt

This text file contains all code used to generate results included in the Evolution journal article. This code is annotated with comments throughout the file.

Johnson_et_al_2021_README.txt

This file contains a brief description of the experimental design and contents of each file, similar to these usage notes.

Funding

National Science Foundation, Award: DEB-1142784

Fordham University

Fordham University Louis Calder Center

National Science Foundation, Award: IOS-1546218