Rate of Adaptation in Large Sexual Populations

TL;DR

This paper models how recombination influences the rate of adaptation in large sexual populations, revealing that recombination accelerates adaptation more significantly as population size and mutation rates increase.

Contribution

It provides a mathematical framework showing that in large populations, the adaptation rate grows logarithmically with mutation rate and is strongly enhanced by recombination.

Findings

Adaptation rate v is linear in NU_b only in small populations.

In large populations, v increases as log(NU_b).

Recombination rate squared increases the adaptation acceleration.

Abstract

Adaptation often involves the acquisition of a large number of genomic changes which arise as mutations in single individuals. In asexual populations, combinations of mutations can fix only when they arise in the same lineage, but for populations in which genetic information is exchanged, beneficial mutations can arise in different individuals and be combined later. In large populations, when the product of the population size N and the total beneficial mutation rate U_b is large, many new beneficial alleles can be segregating in the population simultaneously. We calculate the rate of adaptation, v, in several models of such sexual populations and show that v is linear in NU_b only in sufficiently small populations. In large populations, v increases much more slowly as log NU_b. The prefactor of this logarithm, however, increases as the square of the recombination rate. This acceleration of adaptation by recombination implies a strong evolutionary advantage of sex.