VARIATION IN REACTION NORMS AMONG POPULATIONS OF THE GRASS BOUTELOUA RIGIDISETA.

Area of Science:

• Evolutionary biology
• Plant ecology
• Quantitative genetics

Background:

• Understanding evolutionary processes in natural environments requires investigating reaction norms of quantitative traits.
• Reaction norms describe how a genotype's phenotype changes across different environments.

Purpose of the Study:

• To examine genetic differences in reaction norms for various traits in eight populations of the grass Bouteloua rigidiseta.
• To assess how competition influences the size-specific fecundity of different B. rigidiseta populations.

Main Methods:

• Utilized clonal replicates of genotypes from eight B. rigidiseta populations.
• Planted genotypes in a common garden experiment with two competition levels: no competition and high competition (surrounded by Erioneuron pilosum).
• Measured genetic differentiation and reaction norms for size-specific fecundity (spikelet clusters per tiller number).

Main Results:

• Populations exhibited significant genetic differentiation for multiple traits.
• Detected genetic variation in reaction norms for size-specific fecundity among populations.
• Observed differential responses to competition, with some populations showing reduced fecundity under competition and others less affected.

Conclusions:

• Divergence in reaction norms for size-specific fecundity suggests evolutionary differentiation among B. rigidiseta populations.
• This divergence may stem from past natural selection, potentially involving the costs of phenotypic plasticity, or from genetic drift.
• Highlights the role of plasticity and environmental interactions in shaping plant population evolution.