PT  - JOURNAL ARTICLE
AU  - Andrew D. Foote
AU  - M. Thomas P. Gilbert
AU  - Shyam Gopalakrishnan
AU  - Marie Louis
AU  - Michael D. Martin
AU  - Phillip A. Morin
AU  - Milaja Nykänen
AU  - Camilla Hjorth Scharff-Olsen
AU  - Laurent Excoffier
TI  - Evidence of long-term purging of mutation load in killer whale genomes
AID  - 10.1101/2021.08.21.457186
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.08.21.457186
4099  - http://biorxiv.org/content/early/2021/08/21/2021.08.21.457186.1.short
4100  - http://biorxiv.org/content/early/2021/08/21/2021.08.21.457186.1.full
AB  - Genomes of high latitude killer whales harbour signatures of post-glacial founding and expansion. Here, we investigate whether reduced efficacy of selection increased mutation load in founder populations, or whether recessive deleterious mutations exposed to selection in homozygous genotypes were purged. Comparing the accumulation of synonymous and non-synonymous mutations across pairs of globally sampled genomes reveals that the most significant outliers are high latitude North Atlantic genomes, which have accumulated significantly fewer non-synonymous mutations than all other populations. Comparisons with the genome of a 7.5-Kyr-old North Atlantic killer whale, inferred to be closely related to the population directly ancestral to present-day Icelandic and Norwegian populations, calibrates the timing of the action of selection on non-synonymous mutations predominantly to the mid-late Holocene. Non-synonymous mutations purged in modern Norwegian killer whale genomes are found as globally shared standing variation in heterozygote genotypes more often than expected, suggesting overdominance. Taken together, our findings are consistent with purging of recessive non-synonymous mutations exposed to selection in founder-associated homozygous genotypes.Competing Interest StatementThe authors have declared no competing interest.