Rapid-cycling Brassica rapa evolves even earlier flowering under experimental drought

Area of Science:

• Evolutionary biology
• Plant science
• Climate change adaptation

Background:

• Climate change, particularly drought, drives rapid evolution in plant populations.
• Plants respond to drought via escape (early flowering) or avoidance (water efficiency).
• The viability of drought escape in already early-flowering populations is uncertain.

Purpose of the Study:

• To investigate rapid adaptive evolution of drought escape in early-flowering Brassica rapa.
• To assess if prior selection for early flowering constrains further adaptation to drought.

Main Methods:

• Experimental evolution of rapid-cycling Brassica rapa (RCBr) under drought and watered conditions for four generations.
• Concurrent growth of ancestral and descendant populations under drought and watered conditions.
• Assessment of evolution, plasticity, and adaptation in flowering time and water-use efficiency.

Main Results:

• Drought-evolved RCBr populations exhibited earlier flowering and lower water-use efficiency compared to controls.
• A trend towards earlier flowering was observed in drought-evolved descendants versus ancestors.
• Earlier flowering under drought was adaptive, increasing fitness and consistent with other studies.

Conclusions:

• Rapid adaptive evolution of drought escape occurred in RCBr, with no apparent constraint from existing early flowering.
• Populations can possess sufficient genetic variation for adaptation even after strong prior selection.
• The study highlights the effectiveness of combining artificial selection, experimental evolution, and resurrection ecology.