Direct and indirect selection on flowering time, water‐use efficiency (WUE, δ13C), and WUE plasticity to drought in Arabidopsis thaliana

• Published in: Ecology and evolution Vol. 4; no. 23; pp. 4505 - 4521
• Main Authors: Kenney, Amanda M., McKay, John K., Richards, James H., Juenger, Thomas E.
• Format: Journal Article
• Language: English
• Published: Bognor Regis John Wiley & Sons, Inc 01.12.2014; BlackWell Publishing Ltd
• Subjects: Adaptation; Arabidopsis thaliana; Biological evolution; Correlation; Drought; Drying; Evolution; Fitness; Flowering; flowering time; Flowers & plants; Genetic diversity; Original Research; Plastic properties; Plasticity; Reproductive fitness; selection; Soil moisture; Soil treatment; Soils; water‐use efficiency
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.1270

Flowering time and water‐use efficiency (WUE) are two ecological traits that are important for plant drought response. To understand the evolutionary significance of natural genetic variation in flowering time, WUE, and WUE plasticity to drought in Arabidopsis thaliana, we addressed the following questions: (1) How are ecophysiological traits genetically correlated within and between different soil moisture environments? (2) Does terminal drought select for early flowering and drought escape? (3) Is WUE plasticity to drought adaptive and/or costly? We measured a suite of ecophysiological and reproductive traits on 234 spring flowering accessions of A. thaliana grown in well‐watered and season‐ending soil drying treatments, and quantified patterns of genetic variation, correlation, and selection within each treatment. WUE and flowering time were consistently positively genetically correlated. WUE was correlated with WUE plasticity, but the direction changed between treatments. Selection generally favored early flowering and low WUE, with drought favoring earlier flowering significantly more than well‐watered conditions. Selection for lower WUE was marginally stronger under drought. There were no net fitness costs of WUE plasticity. WUE plasticity (per se) was globally neutral, but locally favored under drought. Strong genetic correlation between WUE and flowering time may facilitate the evolution of drought escape, or constrain independent evolution of these traits. Terminal drought favored drought escape in these spring flowering accessions of A. thaliana. WUE plasticity may be favored over completely fixed development in environments with periodic drought. Using a combination of experimental manipulation, quantitative genetics, and genetic selection analyses, we investigated the evolutionary significance of natural genetic variation in water‐use efficiency (WUE), flowering time, and WUE plasticity to drought in spring flowering accessions of Arabidopsis thaliana. Our results indicate that strong genetic correlation between WUE and flowering time may facilitate the evolution of drought escape, or constrain independent evolution of these traits. Terminal drought favored drought escape (earlier flowering and lower WUE), rather than a more conservative avoidance strategy in these spring flowering accessions of A. thaliana. Finally, WUE plasticity to drought may be favored over completely fixed development in environments with periodic drought.