Takahē – new genetic research
Takahē are one of Aotearoa New Zealand’s conservation success stories. Now new research has shed light on their evolutionary history.
This article has been republished from The Conversation under Creative Commons licence CC BY-ND 4.0 and is written by Nic Rawlence (Senior Lecturer in Ancient DNA, University of Otago) and Alexander Verry (Researcher, Department of Zoology, University of Otago). It was originally published under the title Humans, rats and dogs pushed the takahē into Fiordland – new genetic research maps its dramatic journey.
Takahē adult and chick
Here an adult is takahē feeding it's two month old chick at Zealandia in 2019. When was old enough, the chick was removed by the Takahē Recovery Programme to become part of the wider takahē breeding population.
Takahē are a striking bird and a national treasure in Aotearoa New Zealand. But the history and origin story of this flightless swamp hen have become a point of scientific debate.
Our latest research uncovered the significant impact of humans and past climate change on takahē. Genetic analysis has also revealed that takahē are closely related to their extinct North Island cousin, the moho, contrary to previous research and established ideas.
So what is the story behind this large, prehistoric bird, once believed to be extinct? And how might this new knowledge improve efforts to protect the unique species?
A debated origin story
The evolutionary history of takahē and moho has long puzzled scientists. Previous genetic analysis of small fragments of DNA suggested they were not close relatives. Instead, it was believed they descended from two separate arrivals to New Zealand by an ancient species of swamp hen.
This evolutionary history has become conventional wisdom. But it’s different to the origin story of the majority of New Zealand’s birds with related species in the North and South Islands (such as tīeke and kōkako). Most New Zealand birds descend from a single colonisation event, not two.
Read more: How did ancient moa survive the ice age – and what can they teach us about modern climate change?
Our new research has upended the takahē origin story. Using palaeogenetic techniques we sequenced takahē and moho DNA from fossil, archaeological, historical and living individuals to reconstruct their evolutionary history.
Our findings suggest the Australian or Pacific swamp hen ancestor of takahē and moho arrived in New Zealand four million years ago, as the previously forested landscape began to open up with a cooling climate .
Around 1.5 million years ago, a land bridge between the North and South Islands allowed the now possibly flightless swamp hen to evolve into takahē in the south, and the taller and slighter moho in the north. This land bridge eventually eroded with the development of Cook Strait around 500,000 years ago.
Pūkeko – a great disperser
Purple swamp hens like the pūkeko ( Porphyrio porphyrio melanotus ) are great dispersers, having colonised isolated islands throughout the Pacific 4 million years ago.
Ice ages and human arrival
Our genetic analyses and the fossil records show takahē were restricted to isolated areas in the northwestern and perhaps southern South Island at the height of the last ice age – 29,000 to 19,000 years ago.
As the climate warmed, takahē shifted their distribution to eastern and southern regions. The takahē in the northwest South Island (where the Heaphy Track is today) went locally extinct.
However, the biggest impact on takahē came with the arrival of East Polynesian colonists in the late 13th century. Over-hunting, habitat destruction and predation from kiore (Polynesian rats) and kurī (Polynesian dogs) resulted in the loss of takahē everywhere except Fiordland.
This dramatic contractio n and population bottleneck resulted in a small and inbred population with little to no genetic variation. There is no evidence of the genetic lineage (a serie s of mutations or changes in the genetic code which connect an ancestor to its descendants) of living takahē in any archaeological or fossil specimens we examined.
This lineage may have only occurred in Fiordland, or was extremely rare in takahē and swept to dominance in this small population.
Another possibility suggests this lineage occurred spontaneously – much like the genetic mutation in Queen Victoria that gave rise to haemophilia in members of Europe’s royal families.
We know from historical records that the arrival of Europeans and their furry companions no doubt resulted in further restriction of already rare takahē to the Murchison Mountains in Fiordland. However, we don’t see any further genetic bottleneck at this point, as the damage had already been done by earlier human activity.
The moho suffered the same fate as takahē, with the last probable sighting in the late 1800s. The demise of moho and the near extinction of takahē opened up a job vacancy in the ecosystem, allowing the pūkeko to colonise New Zealand from Australia around 500 years ago.
Human impacts on biodiversity
Successive waves of human arrival in New Zealand had a dramatic impact on biodiversity. This schematic shows the impact of introduced mammalian predators (including humans) on medium-large sized vertebrates – mostly bird species.
Extinct species include but are not limited to the following: (a) penguins; (b) shags; (c,k,l) waterfowl including geese, swans and ducks; (d) large flightless moa; (e) eagles; (f) pinnipeds such as rāpoka sea lion and ihupuku southern elephant seals; (g,j,m,p,t) rails; (h) reptiles and frogs; (i) harriers; (n) ravens; (o) shearwaters; (q) snipe; (r) quails; and (s) bitterns. Predators introduced by East Polynesians (1) include Polynesian dog or kurī (2), and Pacific rat or kiore (3); and those introduced by Europeans (4), which included pigs (5), Norway rats (6), cats (7), brushtail possums (8), ship rats (9), and mustelids including ferrets, stoats and weasels (10).
Schematic from Greig K and Rawlence NJ (2021) The Contribution of Kurī (Polynesian Dog) to the Ecological Impacts of the Human Settlement of Aotearoa New Zealand. Front. Ecol. Evol . 9:757988. Doi: 10.3389/fevo.2021.757988 .
Download a PDF of this image here .
Improving conservation management
The growing field of conservation palaeontology uses the fossil record to inform conservation management decisions. It is especially important for endangered animals where human impact has masked their true biological heritage.
Kea, despite appearances, are not an alpine bird. Likewise, the ideal habitat of takahē is not tussock. Rather, the fossil record suggests takahē preferred border habitats such as the edges of forests, grasslands and shrublands, where one habitat transitions to another.
Conservation palaeontology can and should be used to determine the range of suitable habitats across the country, based on the preferences of prehistoric takahē. This can be married with effective predator control to support takahē populations .
It has long been known that takahē underwent a population bottleneck upon human arrival, but what surprised us was its scale. Our research highlights the need for conservation efforts to maximise the amount of genetic variation passed down to each generation, and to minimise the amount and consequent impacts of inbreeding.
Although threats to our native wildlife exist in the here and now, the past can be a key to future efforts to conserve our precious biodiversity.
Nature of science
The story of the takahē re-discovery and the on-going research into its DNA demonstrates that science is constantly discovering new facts and evidence to grow the understanding of the world around us. Later discoveries and research can change a theory, and this should be viewed as a strength rather than a weakness. Takahē research demonstrates two of the fundamental aspects of science – the tentative nature of scientific knowledge and the role of evidence in supporting new scientific claims.
Related content
Learn more about the takahē and its relatives in the article The takahē’s evolutionary history . Use this introductory article to explore the wide range of resources we have on takahē. Takahē – a context for learning and Planning pathways using takahē resources have links to resources and student activities to help teachers.
Read about research that compared DNA barcodes of swamphens from different countries to find out how pūkeko, takahē and moho are related.
The Science Learning Hub team has curated 2 collections of resources related to takahē. Log in to make these collections part of your private collection – just click on the copy .
Takahē – conservation and ecology supports NZC Living World levels 2 and 3 with notes on key science concepts and planning.
Takahē – science capabilities matches resources with specific capabilities. Notes provide questions, which in turn provide practice in using and understanding the capabilities.
See these other articles written by Dr Nic Rawlence.
Useful links
Find out more about some of the research mentioned in this article:
See the South Island takahē entry on the New Zealand Birds Online website.
Alexander J. F. Verry, Eduard Mas-Carrió, Gillian C. Gibb, Ludovic Dutoit, Bruce C. Robertson, Jonathan M. Waters, Nicolas J. Rawlence, Ancient mitochondrial genomes unveil the origins and evolutionary history of New Zealand's enigmatic takahē and moho. Molecular Ecology 2023. https://doi.org/10.1111/mec.17227.
Read this article from The Guardian, August 2023, Prehistoric bird once thought extinct returns to New Zealand wild.
Trewick, S. A. (1997). Flightlessness and Phylogeny amongst Endemic Rails (Aves: Rallidae) of the New Zealand Region. Philosophical Transactions: Biological Sciences , 352(1352), 429–446. http://www.jstor.org/stable/56680.
Listen to this 2023 Radio NZ programme Alison Ballance: the rediscovery and recovery of the takahe.
Read this 2022 article from the Otago Daily Times DNA analysis solves mystery of wattle bird evolution dividing kokako, huia and tieke.
Kieren J. Mitchell, Nicolas J. Rawlence, Examining Natural History through the Lens of Palaeogenomics, Trends in Ecology & Evolution , Vol 36, Issue 3, March 2021. DOI: https://doi.org/10.1016/j.tree.2020.10.005.
'Wellington Land District', from An Encyclopaedia of New Zealand , edited by A. H. McLintock, originally published in 1966, Te Ara – the Encyclopedia of New Zealand.
Karen Greig, Nicolas J. Rawlence. The Contribution of Kurī (Polynesian Dog) to the Ecological Impacts of the Human Settlement of Aotearoa New Zealand. Frontiers in Ecology and Evolution , Vol 9, 2021. https://doi.org/10.3389/fevo.2021.757988.
David B. McWethy, Janet M. Wilmshurst, Cathy Whitlock, Jamie R. Wood, Matt S. McGlone (2014) A High-Resolution Chronology of Rapid Forest Transitions following Polynesian Arrival in New Zealand. PLoS ONE 9(11): e111328. https://doi.org/10.1371/journal.pone.0111328.
Read this The Conservation article from 2017, also written by Nic Rawlence: The legend of Poūwa: ancient myths of New Zealand's black swan confirmed by fossil DNA.
Discover more about haemophilia in European royalty in this Wikipedia entry.
Rawlence NJ, Scofield RP, McGlone MS and Knapp M (2019) History Repeats: Large Scale Synchronous Biological Turnover in Avifauna From the Plio-Pleistocene and Late Holocene of New Zealand. Frontiers in Ecology and Evolution , Vol 7:158. https://doi.org/10.3389/fevo.2019.00158.
Read about the pūkeko, one of the most recognised native birds in New Zealand, on the Department of Conservation website.
See the kea entry on the New Zealand Birds Online website.
Martini, D., Dussex, N., Robertson, B.C., Gemmell, N.J. and Knapp, M. (2021), Evolution of the “world’s only alpine parrot”: Genomic adaptation or phenotypic plasticity, behaviour and ecology? Molecular Ecology , 30: 6370-6386. https://doi.org/10.1111/mec.15978.
Additional link
In this Radio NZ interview Dr Nic Rawlence, who co-authored the research, speaks about how the takahe are helping climate change research.
Acknowledgements
This article was written by Nic Rawlence (Senior Lecturer in Ancient DNA, University of Otago) and Alexander Verry (Researcher, Department of Zoology, University of Otago). The article was originally published in The Conversation , 5 December 2023. Read the original article .
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