Australia can no longer lay claim the origins of the New Zealand kiwi, with research published in the journal Science showing the kiwi’s closest relative is not the emu as was previously thought.
Ironically, the diminutive kiwi’s closest relative turns out to be the extinct Madagascan elephant bird – a 2-3 metre tall, 275 kg giant. And surprisingly, the study concluded, both of these flightless birds once flew.
“We recently found fossils of small kiwi ancestors, which we suggest might have had the power of flight not too long ago,” says co-author Flinders University biological scientist Dr Trevor Worthy.
“The genetic results back up this interpretation, and confirm that kiwis were flying when they arrived in New Zealand.
“It also explains why the kiwi remained small. By the time it arrived in New Zealand, the large herbivore role was already taken by the moa, forcing the kiwi to stay small, and become insectivorous and nocturnal.”
The new study, led by the University of Adelaide’s Australian Centre for Ancient DNA (ACAD), solves a 150-year-old evolutionary mystery about the origins of the giant flightless “ratite” birds, such as the emu and ostrich, which are found across the southern continents. This group contains some of the world’s largest birds, including the extinct giant moa of New Zealand and elephant birds of Madagascar.
The different “ratite” species, long thought to have formed as the flightless birds, were isolated by the drift of the southern continents over the last 130 million years.
Complete mitochondrial genomes rebuilt from ancient DNA extracted from bones of two elephant birds held by the Museum of New Zealand, Te Papa Tongarewa, have revealed a close genetic connection with the kiwi, despite the striking differences in geography, morphology and ecology between the two.
In an interesting twist, morphological data, which on its own does not recover an elephant bird-kiwi relationship, when analysed with the genetic data improved the support for the relationship.
“So morphology does corroborate the molecular evidence,” said Dr Worthy.