The effect of age and sex on the rate of de novo mutations in barn owls

Abstract

The rate of new mutations is the ultimate source of genetic variation, and thus, a fundamental quantity in evolution. Mutation rates vary across the tree of life, influenced by selection pressures and life-history traits. Within species, mutation rates and types show subtle differences between sexes as well as a positive association with parental age. Most of the direct estimates come from a few mammal species, often primates, and their generality has not been fully realised. Using 33 parent-offspring trios, we investigate the mutation rate in the barn owl (Tyto alba) and show that this species has a mutation rate of 5.6 x 10-9, matching rates of passerine species with a similar generation time of 2-3 years. Using different phasing methods we show that fathers pass on twice as many mutations as mothers and identify subtle differences in the sex-specific spectra of mutations. We also find that the number of mutations increases with paternal age, bringing direct evidence for germline senescence in birds. While across-species mutation rates and types appear conserved, the potential for within species variation due to age is substantial.