Limits to Adaptation in Partially Selfing Species.

Area of Science:

• Evolutionary biology
• Population genetics

Background:

• Haldane's sieve predicts recessive beneficial alleles fix less often in outcrossing populations.
• Selfing organisms bypass Haldane's sieve, favoring recessive allele fixation via rapid homozygosity.

Purpose of the Study:

• Investigate how selfing and outcrossing affect fixation probabilities of beneficial alleles under linked selection.
• Determine the impact of recombination and selective sweeps on adaptation rates in varying selfing rates.

Main Methods:

• Mathematical modeling of allele fixation probabilities.
• Analysis of selective sweeps and linked mutations.
• Comparison of adaptation rates in selfing versus outcrossing populations.

Main Results:

• Loss of weaker adaptive alleles during initial sweeps significantly hinders fixation in highly selfing organisms.
• Selective interference in selfing populations can negate the advantage of not facing Haldane's sieve.
• Outcrossing populations show a greater ability to fix weak beneficial mutations across dominance types.

Conclusions:

• Reduced recombination in selfing organisms can significantly limit adaptation.
• The interplay between selfing, linked selection, and mutation dominance shapes evolutionary trajectories.
• Outcrossing may offer advantages in fixing beneficial mutations, particularly under high mutation rates.