Kākāpō. Credit: Department of Conservation, CC BY 2.0. <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons.

Genome sequencing shows olive feather colouration in New Zealand’s kākāpō evolved around the same time as two now-extinct predators.

Aotearoa New Zealand’s flightless parrot, the kākāpō, evolved two different colour types to potentially help them avoid detection by a now-extinct apex predator according to Lara Urban at Helmholtz AI, Germany and colleagues from the Aotearoa New Zealand Department of Conservation and the Māori iwi Ngāi Tahu.

The kākāpō (Strigops habroptilus) is a nocturnal, flightless parrot endemic to New Zealand. It experienced severe population declines after European settlers introduced new predators.

By 1995 there were just 51 individuals left, but intense conservation efforts have helped the species rebound to around 250 birds. Kākāpō come in one of two colours – green or olive – which occur in roughly equal proportions.

To understand how this colour variation evolved and why it was maintained despite population declines, researchers analysed genome sequence data for 168 individuals, representing nearly all living kākāpō at the time of sequencing.

They identified two genetic variants that together explain colour variation across all the kākāpō they studied.

The kākāpō individual Hoki as an example of the green feather colour polymorphism. Credit: Lydia Uddstrom, New Zealand Department of Conservation, CC-BY 4.0. <https://creativecommons.org/licenses/by/4.0/>

Scanning electron microscopy showed that green and olive feathers reflect slightly different wavelengths of light because of differences in their microscopic structure.

The researchers estimate that olive coloration first appeared around 1.93 million years ago, coinciding with the evolution of two predatory birds: Haast’s eagle and Eyles’ harrier.

Computer simulations suggest that whichever colour was rarer would have been less likely to be detected by predators, explaining why both colours persisted in the kākāpō population over time.

The results suggest that kākāpō colouration evolved due to pressure from apex predators that hunted by sight. This variation has remained even after the predators went extinct, around 600 years ago.

The authors argue that understanding the origins of kākāpō colouration might have relevance to the conservation of this critically endangered species.

They show that without intervention, kākāpō colour variation could be lost within just 30 generations, but it would be unlikely to negatively impact the species today.

Co-author and conservationist Andrew Digby said: “By using a comprehensive genomic library for the species, we have explained how the current colour morphs of kākāpō might be a result of pressure from extinct predators.

“Using genomics to understand the current significance of such characteristics is important as we seek to restore the mauri (life force) of kākāpō by reducing intensive management and returning them to their former habitats.”

The study is published in PLOS Biology.,