Self-fertilization reverses the direction of selection on recombination

Recombination, a fundamental process in genetics, is believed to be shaped by various factors, including the mating system. A new study offers experimental evidence on how self-fertilization impacts the evolution of a recombination modifier. Researchers utilized experimental populations of Caenorhabditis elegans, a species that produces offspring through self-fertilization, and observed the effects of varying selfing rates on the rec-1 mutant.

This mutant is known to redistribute genetic crossovers, making certain regions of the chromosome more diverse while others become less so.

The findings reveal that increasing selfing rates reverses the selective pressure exerted on the rec-1 mutant, shifting it from positive to negative. This surprising outcome is attributed to an expansion of the genomic region over which the rec-1 modifier remains associated with its original genetic combinations. Through simulations, scientists explain this phenomenon by the recombination modifier favoring the conservation of its original distribution pattern, even as selfing rates increase.

These results challenge existing theoretical models of recombination evolution under different mating systems. Previous models assumed that recombination landscapes would remain uniform regardless of the mating system. However, this study demonstrates that selfing can fundamentally alter the evolutionary trajectory of recombination modifiers, revealing a mechanism previously unknown to scientists.

This discovery not only expands our understanding of recombination's role in evolution but also highlights the intricate interplay between genetic diversity and mating systems.