INBREEDING DEPRESSION DOESN'T MATTER: THE GENETIC BASIS OF MATING-SYSTEM EVOLUTION

Area of Science:

• Evolutionary Biology
• Genetics
• Plant Sciences

Background:

• Mating-system evolution models often assume inbreeding depression is independent of mating-system loci genotypes.
• Inbred populations develop associations between genotypes at different loci.
• Heterozygosity at mating-type loci increases heterozygosity at fitness loci compared to random individuals.

Purpose of the Study:

• To investigate the role of genotype-fitness associations in mating-system evolution.
• To evaluate the adequacy of inbreeding depression as a sole descriptor of fitness in selfing populations.
• To model the evolution of self-fertilization in plants considering genetic linkage.

Main Methods:

• Developed a modifier model for the evolution of self-fertilization in plants.
• Analyzed the impact of genetic associations between mating-type and fitness loci.
• Simulated scenarios with varying levels of inbreeding depression and genetic architectures.

Main Results:

• Inbreeding depression is not an adequate descriptor of relative fitness for inbred versus outbred progeny.
• Intermediate self-fertilization rates can be favored when inbreeding depression results from overdominant loci (even <30%).
• Mutants promoting outcrossing can invade selfing populations with low inbreeding depression (as low as 1%) if it stems from overdominance.
• Selfing can evolve in random-mating populations if inbreeding depression results from recessive lethals (even >70%).

Conclusions:

• Genetic associations between mating-type and fitness loci are crucial for understanding mating-system evolution.
• Inbreeding depression's impact on fitness is context-dependent, influenced by the genetic basis of deleterious alleles.
• Models must incorporate genetic linkage to accurately predict the evolution of selfing and outcrossing rates.