In theory, genomic erosion can be reduced in fragile “recipient”
populations by translocating individuals from genetically diverse
“donor” populations. However, recent simulation studies have argued
that such translocations can, in principle, serve as a conduit for new
deleterious mutations to enter recipient populations. A reduction in
evolutionary fitness is associated with a higher load of deleterious
mutations and thus, a better understanding of evolutionary processes
driving the empirical distribution of deleterious mutations is crucial.
Here, we show that genetic load is evolutionarily dynamic in nature and
that demographic history greatly influences the distribution of
deleterious mutations over time. Our analyses, based on both
demographically explicit simulations as well as whole genome sequences
of potential donor-recipient pairs of Montezuma Quail (Cyrtonyx
montezumae) populations, indicate that all populations tend to lose
deleterious mutations during bottlenecks, but that genetic purging is
pronounced in smaller populations with stronger bottlenecks. Despite
carrying relatively fewer deleterious mutations, we demonstrate how
small, isolated populations are more likely to suffer inbreeding
depression as deleterious mutations that escape purging are homogenized
due to drift, inbreeding, and ineffective purifying selection. We apply
a population genomics framework to showcase how the phylogeography and
historical demography of a given species can enlighten genetic rescue
efforts. Our data suggest that small, inbred populations should benefit
the most when assisted gene flow stems from genetically diverse donor
populations that have the lowest proportion of deleterious mutations.
Genetic load and mortality in partially inbred populations of swine
