Data for Escaping bottlenecks: the demographic path to genetic recovery in koalas (Phascolarctos cinereus)

Population bottlenecks can lead to evolutionary dead-ends by eroding genetic diversity and intensifying inbreeding. While theory predicts possible escape routes, direct observations of this process are rare. Using whole-genome data from 418 koalas, we found that populations with higher genetic diversity harbored the greatest mutational loads and had declining effective population sizes (Ne), whereas historically bottlenecked, but recovering, populations displayed reduced mutational load, exhibited increasing Ne, and regenerated new, rare, variants. We conclude this pattern is due to rapid demographic expansion, which reshuffled genetic variation through recombination and affected Ne more quickly than it did conventional diversity metrics. Our findings suggest recovery of bottlenecked populations can occur through rapid demographic growth and that this can re-establish evolutionary potential in threatened populations.