Inbreeding depression maintained by recessive lethal mutations interacting with stabilizing selection on quantitative...

Area of Science:

• Evolutionary genetics
• Population genetics
• Quantitative genetics

Background:

• Mutations have varying fitness effects, categorized as early-acting strongly deleterious recessive or late-acting mildly deleterious.
• Understanding these effects is crucial for analyzing genetic variation and inbreeding depression in populations.

Purpose of the Study:

• To analyze the bimodal distribution of fitness effects of mutations and standing genetic variation.
• To investigate the combined effects of lethals, selfing, and stabilizing selection on genetic variance and mutation purging.

Main Methods:

• Utilized the Kondrashov model for lethals (K).
• Integrated the infinitesimal model for selfing (IMS) and the Gaussian allele model (GAM) for quantitative genetic variance.
• Analyzed combined models (KIMS and KGAM) under stabilizing selection.

Main Results:

• High mutation rates and weak stabilizing selection create interactions between early and late inbreeding depression.
• Alternative stable equilibria can exist at intermediate selfing rates.
• Stabilizing selection can either facilitate or interfere with the purging of nearly recessive lethals, depending on selfing rates.

Conclusions:

• The interplay between quantitative genetic variance evolution and purging of lethals is significant.
• Stabilizing selection's effect on purging depends on the relative thresholds for quantitative variance and lethal purging.
• Model predictions highlight complex dynamics in the maintenance of genetic variation and the impact of inbreeding.