A test of the long term efficiency of genetic rescue with Drosophila
melanogaster
Abstract
Genetic rescue is increasingly viewed as a promising but underutilized
conservation strategy to mitigate inbreeding depression and restore
genetic diversity. Yet, empirical evidence supporting its long-term
efficacy is limited to a few generations. Here, we conducted an
experiment with Drosophila melanogaster to test the long-term efficiency
of genetic rescue in reducing population extinction risk. A recently
captured wild population was maintained in the laboratory with a large
census size (the base population, BP). Thirty smaller populations of N =
50 individuals (N50) were founded from the BP and maintained for 31
generations. Subsequently, three sets of 54 lines with N = 8 individuals
each, were founded from these N50 populations and maintained for 33
generations. One set served as a control (non-rescued lines), while the
other two sets were rescued using a single male introduced in two
consecutive generations either from the BP (rescued-BP) or from the N50
(rescued-N50) populations. An analysis of pupae productivity at the time
of the foundation of the lines showed substantial purging of the
inbreeding load in the N50 populations. No significant differences in
pupae productivity were found between the non-rescued lines and
rescued-BP lines at generation 9. However, extinction rates were lower
for the latter. Whole-genome sequencing of 12 individuals from a
non-rescued line and 12 from a rescued-BP line revealed fewer
deleterious allele copies and a lower inbreeding in the rescued one. Our
results highlight the effectiveness of genetic rescue in reducing the
extinction rate by efficiently selecting advantageous alleles
responsible for hybrid vigour, purging of the introduced genetic load,
and introducing adaptive potential.