PT  - JOURNAL ARTICLE
AU  - Thomas LaBar
AU  - Christoph Adami
TI  - Evolution of Drift Robustness in Small Populations
AID  - 10.1101/071894
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 071894
4099  - http://biorxiv.org/content/early/2017/06/08/071894.short
4100  - http://biorxiv.org/content/early/2017/06/08/071894.full
AB  - Most mutations are deleterious and cause a reduction in population fitness known as the mutational load. In small populations, weakened selection against slightly-deleterious mutations results in an additional fitness reduction. Many studies have established that populations can evolve a reduced mutational load by evolving mutational robustness, but it is uncertain whether small populations can evolve a reduced susceptibility to drift-related fitness declines. Here, using mathematical modeling and digital experimental evolution, we show that small populations do evolve a reduced vulnerability to drift, or “drift robustness”. We find that, compared to genotypes from large populations, genotypes from small populations have a decreased likelihood of small-effect deleterious mutations, thus causing small-population genotypes to be drift-robust. We further show that drift robustness is not adaptive, but instead arises because small populations preferentially adapt to drift-robust fitness peaks. These results have implications for genome evolution in organisms with small population sizes.