Exploring indirect selection on a modifier of meiotic crossover position in C. elegans

Henrique Teotonio

Institut de Biologie, Ecole Normale Supérieure, Paris, France

teotonio@bio.ens.psl.eu

Genetic modifiers of sex and recombination have been described, but the selective pressures act-ing on them and their effect on adaptation to novel environments remain unclear. I will provide an overview about experimental studies on the evolution of sex and recombination and then describe the results of evolution experiments using a mutant that modifies meiotic crossover positions and the recombination rate landscape of the nematode Caenorhabditis elegans. Our results show that adaptation to a novel environment is impaired by the modifier that decreases recombination rates in genomic regions containing fitness variation. However, the modifier that impairs adaptation is indirectly favored by selection because it increases recombination in its chromosomal vicinity and benefits from the local associations it establishes with adaptive genotype combinations. Simulation and experimental results further confirm that the evolution of recombination is caused by the dis-ruption of the associations between beneficial and deleterious alleles, and that the strength and direction of indirect selection depends not only on genomic location but also on any factor changing the degree of linkage disequilibrium between fitness loci such as the degree of self-fertilization. Overall, our results demonstrate that indirect selection acting on recombination modifiers is decou-pled from its consequences on polygenic adaptation.

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