Reconstructed Moa Genome May Move the Meaty Bird Closer to De-Extinction
The first nuclear genome for an extinct moa species begins a new chapter in research on these big bygone birds, possibly improving the chances that they will one day be resurrected.
Many mysteries have surrounded the nine species of extinct moa from New Zealand, but the fate of the big birds is a scientific no-brainer. Shortly after Polynesians settled New Zealand in the late 13th century, the relatively easy to hunt, meaty and flightless birds went extinct. Habitat loss and impacts associated with introduced species further helped to seal their doom.
Gone for well over 700 years, moa appear to be on a path to de-extinction. That is because scientists have just assembled the first nuclear genome for an extinct moa species: the little bush moa (Anomalopteryx didiformis). The genome, albeit a partial draft and published via the biology preprint server bioRxiv, would be critical to possible resurrection of this species and other moa.
"The sequencing of the partial, draft little bush moa genome is a defining moment in our understanding of the evolutionary history of New Zealand's unique biodiversity," Nic Rawlence, director of the Otago Paleogenetics Laboratory, told Seeker.
"This has been a holy grail in ancient DNA — some of the first ancient DNA studies were on moa — and will allow scientists to bring the power of the genomic revolution to answer some of the big questions regarding ratite evolution, moa evolution, and how moa responded to New Zealand's dynamic geological and climatic history, and ultimately the human arrival that led to their extinction," continued Rawlence, who is also a lecturer in ancient DNA at New Zealand’s University of Otago.
He added, "It opens the door to sequence more moa genomes, of other moa species, and genome of other extinct ratites like elephant birds."
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Ratites include not only moa and elephant birds, but also ostriches, rheas, tinamous, emus, cassowaries, and kiwis. The two largest moa grew to about 12 feet in height and weighed around 510 pounds. The elephant bird Aepyornis could grow to more than 10 feet tall and weighed as much as 1,100 pounds.
By today's standards, the little bush moa was hardly small; it stood more than 4.3 feet tall and weighed approximately 66 pounds. Specimens of the birds were collected by Trevor "Mr. Moa" Worthy, a paleozoologist at Flinders University in Australia, and are held in collections at the Royal Ontario Museum.
For the new study, lead author Alison Cloutier of Harvard University and her team extracted DNA from a single toe bone from one of the birds. They next utilized high-throughput sequencing techniques, which allow sequencing of hundreds of thousands of strands of DNA at once. The authors explain that they then recovered almost 900 megabytes of the moa nuclear genome by “mapping reads to a high quality reference genome for the emu (Dromaius novaehollandiae)."
The researchers additionally isolated 40 repeating tracts of DNA, known as polymorphic microsatellites. These are spread throughout the genome and are sufficiently short to allow amplification even in degraded fossil samples.
The authors also recovered coding sequences for a suite of genes potentially associated with flightlessness in moa and other ratites, but there was a very surprising discovery.
Rawlence said that "the majority of the genes for wings are present in the moa genome, so it looks like moa's complete lack of wings is not a simple case of gene loss."
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In a second study conducted by the same research team with other colleagues, Cloutier, lead author Timothy Sackton of Harvard, and their co-authors determined that flight was lost at least three separate times over the course of ratite evolution. Since the new genome shows that the birds did not simply lose genes associated with flight, the researchers now believe that gene regulation — not loss — led to the molecular changes underlying flightlessness.
Yet another study led by Cloutier and Sackton utilized the new little bush moa genome, along with other DNA data, to resolve the phylogeny of certain extant flightless birds. The scientists determined that rheas are sister taxa to kiwis, emus, and cassowaries. This means that rheas are the closest relatives of the latter three groups. Kiwis are perhaps the most unlikely of the four types, given that these birds are just the size of a domestic chicken.
Rheas, kiwis, emus, and cassowaries are still very much in the land of the living, opening up the possibility that the little bush moa genome could be inserted into one of their eggs.
The Genetic Rescue Foundation, based in New Zealand, has the stated goal of creating "the most detailed moa genome possible in order to advance our understanding of one of the most iconic birds that ever lived."
Based on "project milestones" listed at the foundation's website, founder David Iorns has made progress in funding the project and in obtaining and sequencing samples. The new little bush moa genome would seem to advance the effort, which could include resurrecting this species.
The foundation published an essay by Amy Fletcher of the University of Canterbury. She is an advisory board member of the Moa Revival Project. Fletcher mentions the challenges in finding high quality "ancient DNA" and "a well-preserved moa bone" — challenges that Cloutier, Sackton and their colleagues have since seemingly overcome.
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Fletcher admits that the idea of bringing back the moa "is a controversial one that sparks a great deal of public and scientific debate." Nevertheless, she adds, "If we resist the notion that extant and extinct species are in competition with each other, and focus instead on biological and environmental enrichment in the deepest sense, de-extinction could prove a journey into the past that ensures our environmental future."
Rawlence agrees that it would be beneficial to de-extinct moas, "given the New Zealand ecosystem has not realized they have gone extinct and there are now many lost ecological connections that moa were at the heart of."
He quickly added, however, that in order to bring moa back, "we would have to bring back their microbiome and parasites — so moa could function in the New Zealand ecosystem — many of which went extinct with the moa. Just a bit of a tall order, I think."
Biologist Joseph Bennett of Carleton University told Seeker that there are at least five reasons why de-extinction of moa and other long-gone animals is still being pursued by certain researchers and organizations.
Those who achieve such a breakthrough might also stand to gain substantial money tied to everything from television deals to ticket sales to a Jurassic Park-like zoo. On a more humanitarian note, "desperation," he said, is also fueling interest in de-extinction work.
"Some argue that we should use any tool at our disposal to save biodiversity," he explained.
In a study published last year in the journal Nature Ecology & Evolution, Bennett and his team determined that spending already limited resources on de-extinction could lead to net biodiversity loss. Even if private agencies have deep pockets, he argued they would be better off spending their money on living, threatened species.
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Philip Seddon of the University of Otago agreed. "The focus must remain on keeping all of the species we still have," he told Seeker.
Seddon said de-extinction technologies could be used to improve the conservation status of threatened species before they go extinct. For example, scientists could re-engineer lost genetic diversity into living populations using information from museum specimens. This could help to overcome inbreeding problems due to genetic bottlenecks.
Conservationists have been considering applying such techniques to the race to save highly endangered animals like the northern white rhino. A recent health scare affecting the last known male of the species also has researchers scrambling to create northern white rhino embryos through in vitro fertilization. So far, they have not succeeded.
The ultimate goals of Cloutier and her team concerning moa remain less clear, at least for now. Cloutier informed Seeker that she and her colleagues are refusing to comment publicly on their findings until their studies have gone through the peer review process. At minimum, that can take a few months, but will likely be much longer.