Plasticity versus canalization: population differences in the timing of shade-avoidance responses

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Phenotypic plasticity and environmental specialization are shaped by environmental cue reliability and phenotypic costs.
• Plant competitive strategies are influenced by these factors, particularly in response to light quality cues.

Purpose of the Study:

• To investigate the relationship between environmental cue reliability and costs in the evolution of plant competitive strategies.
• To examine genetic differences in elongation and plasticity in Abutilon theophrasti populations under varying light conditions.

Main Methods:

• Experimental light treatments (full sun, neutral shade, foliar shade) were applied to six Abutilon theophrasti populations from different site types.
• Measurements of average elongation and plasticity to foliar-shade cues were taken at seedling and later life-history stages.

Main Results:

• Seedling populations from cornfields showed greater average elongation than those from other sites, potentially an adaptation to early shading.
• Simulated foliar shade induced greater elongation than average population differences, at a significant allocation cost.
• Later-stage populations from cornfields exhibited reduced plasticity to light quality compared to weedy populations.

Conclusions:

• Reliable environmental cues may favor phenotypic plasticity, enabling adaptive responses to competition but incurring costs.
• Reduced plasticity can evolve when environmental cues do not reliably predict adaptive outcomes, as seen in later stages of cornfield populations.
• Phenotypic plasticity may constrain the evolution of specialists by allowing facultative adoption of costly, advantageous phenotypes.