Quantifying natural seasonal variation in mutation parameters with mutation accumulation lines.

Area of Science:

• Evolutionary biology
• Genetics
• Ecology

Background:

• Mutations generate genetic diversity, but their impact on phenotypes, including fitness, is influenced by environmental conditions.
• Natural environments are often heterogeneous, posing challenges for understanding mutation effects.
• Arabidopsis thaliana is a model organism for studying plant genetics and evolution.

Purpose of the Study:

• To assess the contribution of new mutations to phenotypic variation in fitness-related traits across different temporal environments.
• To compare mutational variance with environmental variance in natural settings.
• To evaluate the potential of new mutations to contribute to standing genetic variation in Arabidopsis thaliana.

Main Methods:

• Phenotypic assessment of survival and reproductive success in over 30,000 Arabidopsis thaliana plants from 100 mutation accumulation lines.
• Experiments conducted across four distinct temporal environments at a single field site.
• Statistical analysis to quantify mutational and environmental variance for various traits.

Main Results:

• Environmental variance consistently exceeded mutational variance across all tested traits and environments.
• Mutational variance for some traits showed significant variation between seasons.
• New mutations contributed more to phenotypic variation than predicted based on divergence in natural populations.
• The founder genotype's mean trait values were close to the distribution mean of mutation accumulation lines.

Conclusions:

• Environmental heterogeneity plays a substantial role in phenotypic variation, often overshadowing the effects of new mutations.
• Despite large environmental variance, new mutations can significantly contribute to standing genetic variation.
• The findings suggest that mutations may be more important for long-term adaptation than previously assumed, especially in fluctuating environments.