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Scientists reconstruct the genome of the little bush moa, New Zealand’s extinct avian giant
Using ancient DNA recovered from a fossil bone, scientists have reconstructed a complete genome of the little bush moa, an extinct species of flightless bird that once roamed the forested islands of New Zealand. The work – which includes the first nuclear genome of any moa species – allowed the scientists to determine the bird’s likely population size, and even suggests that the moa’s eyes could detect ultraviolet light. The moas of New Zealand were once some of the world’s largest birds, making their homes in the islands’ dense forests and grasslands as recently as 700 years ago. However, these magnificent giants went extinct after humans colonized New Zealand due to overhunting and the introduction of non-native species, such as Polynesian dogs. In modern times, scientists have learned much about the nine species of moas by analyzing samples of ancient DNA from fossils. Nevertheless, researchers have only just begun to plumb the depths of genetic information available, and many aspects of moa biology remain shrouded in mystery. Now, Scott Edwards and colleagues present the complete genome of the little bush moa (Anomalopteryx didiformis), a small species of moa that was slightly larger than a turkey. They 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. The team 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, Edwards et al. then estimated that the long-term population size of the bush moa was approximately 237,000 individuals. The team 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 light. “Additional nuclear genome assemblies from extinct moa […] will no doubt further enable exploration of the genetic basis of phenotypic traits of these extraordinary birds,” Edwards et al. conclude.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Associate Professor Nic Rawlence, Director, Otago Palaeogenetics Laboratory, University of Otago
The extinct moa of New Zealand are one of our taonga (treasured) species that have fascinated generations of kiwi kids. 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 (the entire genetic blueprint of an individual) 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.
Scott Baker and colleagues, including the late New Zealand scientist Allan Baker (no relation), have just published their in-depth analysis of the little bush moa genome. The genome has been freely available to other researchers since 2018.
Moa are unique among birds in having no wings at all. This genome had previously been used to show that the genetic blueprint for wing formation is correct (it works!) but that the instructions to tell the body when, where, and how much wing to make have been corrupted. The current study backs this up and provides further avenues for future research.
This new study uses the genome to estimate the population size of little bush moa at ~240,000 individuals. This is likely too high, and the authors admit it’s a rough estimate. 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 coloured truffle-like fungi that may have been dispersed by moa. Moa also had sensitivity to bitter foods like other birds.
Most importantly, this little bush moa genome will be a valuable resource that scientists can build upon, like our collaborative research with Manaaki Whenua Landcare Research sequencing the genomes of all nine moa species.
I must also commend the authors for their due diligence in trying to determine where in the South Island the little bush moa bone that contained this taonga genome came from. This is important so appropriate kaitiaki (guardians) from iwi and rūnanga can be determined, to ensure tikanga (cultural practices) are followed for further use of this resource. I applaud the researchers for repatriating this genetic blueprint back to Aotearoa New Zealand. Engagement with mana whenua regarding ancient DNA research on New Zealand animals can be very positive but it can also be challenging and ever evolving, let alone for the bones and skins of living and extinct species housed in overseas museums. This is a positive start for overseas-based researchers working with mana whenua into the future.
Dr Gillian Gibb, Senior Lecturer in Zoology and Ecology, Massey University
It's great to have this genomic resource published, from a specimen which has been in the Royal Ontario Museum in Toronto since the late 1990s.
This is an update on the draft little bush moa genome which was first published as part of Sackton et al (2019), so it is great to see a more in-depth analysis of this genome by itself.
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. 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.
Moa are iconic because of their large size and lack of wings. As has also been shown in many other flightless birds, in moa wing loss is not associated with the pseudogenisation or loss of genes associated with limb development and is much more likely to be the result of many subtle changes in genes and their regulation.
Professor Paul Scofield, Senior Curator Natural History, Canterbury Museum
Since Michael Crichton’s seminal book “Jurassic Park” ignited public imagination about the dream of de-extinction, the idea of sequencing the entire genome of extinct animals has been a cause célèbre in popular media. Whilst huge issues remain with this dream (not least of which is how do we birth such a phoenix), the dream has come one step closer with the publication today of the near-complete (c.85%) genome of the little bush moa (Anomalopteryx didiformis).
This remarkable project was begun by New Zealander Professor Alan Baker and continued by a multinational team led by Professor Scott Edwards at Harvard University. The original specimen was a toe bone in the collection of Auckland Museum that was sampled by Baker in the late 1990s. Technology at the time only allowed a small portion of the genome to be sequenced but (along with many other samples) it gave us great insights into the evolutionary history of moa. We discovered that moa were not kiwi’s closest relative (that was the tinamou of South America) and that the ancestors of moa (and kiwi) were not passengers on “Moas Ark” as it drifted away from Gondwana but in fact probably flew here 45 million years ago. This led to headlines in the Australian press such as “Kiwi are simply Aussies who flew the coop”.
Moa are the only birds that have completely lost their wings. 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. This paper also finds that moa had normal smelling abilities for a bird despite having an unusual configuration of the olfactory lobe in the brain. They also estimated (using the genetic profile) a population size for this species of 240,000 individuals.
A crucial aspect to this paper is the work Edwards and his team have done to consult with Māori. The original work was undertaken in an environment where consultation with tangata whenua was not the norm. It is important to recognise the way Professor Edwards and his team has acknowledged this shortcoming in the earlier work and ensured consultation and consensus on this new work. The team have ensured that the mātauranga (knowledge) will remain in Aotearoa through depositing the data in the Aotearoa Genomics Data Repository.
