Genome-wide diversity in the California condor tracks its prehistoric abundance and decline

Due to their small population sizes, threatened and endangered species frequently suffer from a lack of genetic diversity, potentially leading to inbreeding depression and reduced adaptability.(1) During the latter half of the twentieth century, North America's largest soaring bird,(2) the California condor (Gymnogyps californianus; Critically Endangered(3)), briefly went extinct in the wild. Though condors once ranged throughout North America, by 1982 only 22 individuals remained. Following decades of captive breeding and release efforts, there are now >300 free-flying wild condors and similar to 200 in captivity. The condor's recent near-extinction from lead poisoning, poaching, and loss of habitat is well documented,4 but much about its history remains obscure. To fill this gap and aid future management of the species, we produced a high-quality chromosome-length genome assembly for the California condor and analyzed its genome-wide diversity. For comparison, we also examined the genomes of two close relatives: the Andean condor (Vultur gryphus; Vulnerable(3)) and the turkey vulture (Cathartes aura; Least Concern(3)). The genomes of all three species show evidence of historic population declines. Interestingly, the California condor genome retains a high degree of variation, which our analyses reveal is a legacy of its historically high abundance. Correlations between genome-wide diversity and recombination rate further suggest a history of purifying selection against linked deleterious alleles, boding well for future restoration. We show how both long-term evolutionary forces and recent inbreeding have shaped the genome of the California condor, and provide crucial genomic resources to enable future research and conservation.

Automated summary

The study focused on the genome of the California condor, Andean condor, and turkey vulture, revealing that the California condor genome retains a high degree of variation due to its historically high abundance. Correlations between genome-wide diversity and recombination rate suggest a history of purifying selection against linked deleterious alleles, providing a promising foundation for future restoration efforts.