Testing for local adaptation in Avena barbata: a classic example of ecotypic divergence

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Robert Allard's 1970s research identified two Avena barbata genotypes in California linked to mesic and xeric habitats.
• These genotypes were considered the first molecularly identified ecotypes, but local adaptation was inferred solely from allozyme patterns.

Purpose of the Study:

• To empirically test for local adaptation in Avena barbata ecotypes using reciprocal transplant and quantitative trait locus (QTL) mapping.
• To investigate the genetic basis of performance differences and identify potential trade-offs across environments.

Main Methods:

• Reciprocal transplant experiments with ecotypes and recombinant inbred lines (RILs) in common garden plots.
• Quantitative trait locus (QTL) mapping to identify genes influencing lifetime reproductive success.
• Evaluation of performance across two distinct sites and four growing seasons.

Main Results:

• The mesic ecotype exhibited higher lifetime reproductive success across all environments, despite significant genotype-environment interactions.
• Recombinant inbred lines showed no performance trade-offs across sites or years; fitness correlated positively across environments.
• Selection favored the same alleles at QTL influencing reproductive success in all tested environments.

Conclusions:

• Observations contradict the hypothesis of local adaptation in Avena barbata ecotypes.
• Findings suggest a single genotype is selectively advantageous in both moist and dry conditions.
• An alternative hypothesis of contemporary evolution, involving the spread of a favored genotype, is proposed.