Koala population rebound in southeastern Australia boosts genetic diversity and curbs inbreeding risks.

Key facts

• Koala numbers in Victoria rebounded from ~500 in the early 20th century to nearly 500,000 by 2020.
• Research published on 5 March in Science analysed genetic data from 418 koalas across 27 populations in eastern Australia.
• Rapid population growth has increased beneficial genetic combinations and reduced rates of tooth and testicle malformations in Victorian koalas.
• Northern koalas currently show higher genetic diversity but face a genetic bottleneck due to population decline.
• Cesar Australia evolutionary biologist Collin Aherns compared the recovery pattern to the Roesel’s bush cricket in Sweden, which regained lost genetic diversity in 15 generations.
• University of East Anglia evolutionary geneticist Cock van Oosterhout noted that wild-species data supporting evolutionary recovery theories remain limited.