Abstract
The ubiquity of recombination (and sex) in nature has defied explanation since the time of Darwin1–4. Conditions that promote the evolution of recombination, however, are well-understood and arise when genomes contain more selectively mismatched combinations of alleles across loci than can be explained by chance alone. Recombination remedies this across-loci imbalance by shuffling alleles across individuals. The great difficulty in explaining the ubiquity of recombination in nature lies in identifying a source of this imbalance that is comparably ubiquitous. Here, we look to natural selection itself as a possible source of pervasive imbalance, with the rationale that the ubiquity of natural selection approximates the ubiquity of sex and recombination in nature. Natural selection is fed by heritable variation which may be produced by any number of factors, such as drift, founder effects, migration and mutation. We ask how natural selection, acting on this variation, affects the across-loci imbalance and hence the evolutionary potential of recombination. Remarkably, we find that the effect of natural selection is to always promote the evolution of recombination, on average, independently of the source of the variation that feeds it. We show this is true for both across- and within-population recombination. Our findings suggest that recombination evolved and is maintained more as an unavoidable byproduct of natural selection than as a catalyst.
Competing Interest Statement
The authors have declared no competing interest.