Using ancient DNA recovered from a fossil bone from New Zealand’s South Island, scientists from Harvard University and elsewhere have generated a draft genome for the little bush moa (Anomalopteryx didiformis), one of nine species of flightless birds that once roamed the forested islands of New Zealand.
Moa browsed trees and shrubs within the forest understorey. Image credit: Heinrich Harder.
The extinct moa of New Zealand comprise nine currently recognized species and belong to the bird infraclass Palaeognathae, which encompasses the flightless ratites (ostrich, emu, cassowary, kiwi, rheas, moa, and elephant birds) and the volant, or flying, tinamous.
Extinction of all moa species is thought to have closely followed the Polynesian settlement of New Zealand in the 13th century CE as the result of direct human exploitation compounded by anthropogenic land-use changes and impacts associated with introduced species.
“The extinct moa of New Zealand are one of our taonga (treasured) species that have fascinated generations of kiwi kids,” said Dr. Nic Rawlence, a paleontologist at the University of Otago, who was not involved in the study.
“While we know a lot about the nine different moa species that called Aotearoa home since the advent of ancient DNA, there are still many questions that remain unanswered.”
“Having the nuclear genome of a male little bush moa is a start to delving deeper into what makes moa so special — even if it is a draft, about 85% complete.”
In the new study, Harvard University researcher Scott Edwards and his colleagues assembled both a complete mitochondrial genome and a nuclear genome of a male moa by sequencing ancient DNA and comparing it to a high-quality genome of the related emu.
They first calculated that the size of the moa’s nuclear genome was approximately 1.07 to 1.12 billion bases.
By analyzing genetic diversity in the mitochondrial genome, they then estimated that the long-term population size of the bush moa was approximately 237,000 individuals.
“Recovering the genome for species like the little bush moa is challenging because the amount of degraded ancient DNA you can recover is quite small,” said Dr. Gillian Gibb, a researcher at Massey University, who was not involved in the study.
“In the case of moa, extra challenges exist because the closest living relative with a high-quality genome for comparison diverged about 70 million years ago.”
“Despite this difficulty a large portion of the genome has been recovered, and allows insight into moa evolution.”
The authors also investigated genes involved in the moa’s sensory biology and concluded that the bird likely had a decent sense of smell and harbored receptors in its eye that could sense ultraviolet (UV) light.
“This new study uses the genome to estimate the population size of little bush moa at around 240,000 individuals. This is likely too high, and the authors admit it’s a rough estimate,” Dr. Rawlence said.
“Ecological estimates for moa across the motu (country) are between two to ten birds per square km, with a total population size of 500,000 to 2.5 million moa.”
“The genome also shows that little bush moa had a complex repertoire of smell, matching what is seen looking at moa skulls.”
“Moa were also able to see in the UV spectrum, which could have aided in finding food like our brightly colored truffle-like fungi that may have been dispersed by moa.”
“Moa also had sensitivity to bitter foods like other birds.”
“Moa are the only birds that have completely lost their wings,” added Canterbury Museum’s Professor Paul Scofield, who was not involved in the study.
“This new paper also examines in detail the great mysteries how this happened, concluding that this was not — as had been suggested — due to the loss of the genes that code for wing development.”
“The paper also finds that moa had normal smelling abilities for a bird despite having an unusual configuration of the olfactory lobe in the brain.”
The study was published in the journal Science Advances.
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Scott V. Edwards et al. 2024. A nuclear genome assembly of an extinct flightless bird, the little bush moa. Science Advances 10 (21); doi: 10.1126/sciadv.adj6823
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