The curious genome of the Tuatara, a vulnerable species that is NOT a lizard

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International scientists and Ngātiwai, a Maori tribe, have teamed up to sequence the genome of a rare reptile, the tuatara, uncovering some unique aspects of tuatara evolution. The genome sequence will allow comparative studies to better understand the evolution of the tuatara and its distant relatives: other reptiles, birds and mammals. Shedding light on the biology of the tuatara will help protect this vulnerable species. Credit: Bernard Spragg

Researchers have sequenced the tuatara’s genome, revealing its unique evolutionary history.

Summary

  • International scientists and Ngātiwai, a Maori tribe, have teamed up to sequence the genome of a rare reptile, the tuatara, uncovering some unique aspects of tuatara evolution
  • The genome sequence will allow comparative studies to better understand the evolution of the tuatara and its distant relatives: other reptiles, birds and mammals
  • Shedding light on tuatara biology will help protect this vulnerable species

A global team of researchers has teamed up with the Ngātiwai Maori tribe to sequence the genome of the tuatara, a rare reptile endemic to New Zealand. Their work, published in the scientific journal Nature, lays the groundwork for understanding the evolution of this ancient species and can inform conservation efforts to protect it. The study included collaborators from the University of Otago and the EMBL European Bioinformatics Institute (EMBL-EBI).

With its small, scaly body, pointed tail, and clawed feet, the tuatara seems to tick all the boxes for being a lizard, but it isn’t. This ancient reptile is the sole survivor of its own evolutionary branch on the tree of life, Sphenodontia. Until now, biologists have not reached a consensus on the evolutionary history of tuatara – whether they are more closely related to birds, crocodiles and turtles, or whether they came from a shared ancestor with lizards and snakes.

“Our research confirms that tuatara diverged from the ancestor of lizards and snakes around 250 million years ago,” says Matthieu Muffato, head of analysis of the Comparative Genomics Ensemble at EMBL- EBI. “This long period of independent evolution explains why we discovered that the tuatara genome was so different from that of other vertebrates.”

A biological curiosity

“The tuatara genome is considerably larger than the human genome, and it has a unique constitution. It contains a lot of repetitions DNA segments that are unique to the species and have no known function,” says Fergal Martin, Vertebrate Annotation Coordinator at EMBL-EBI.

The tuatara genome sequence revealed a number of aspects of this reptile’s lifestyle. Although tuatara are primarily nocturnal animals, their DNA carries a large number of genes involved in color vision, which could help diurnal juveniles escape predators.

If they survive the vagaries of their youthful life, tuatara can live for over 100 years. Scientists examining some of the genes involved in protecting the body against aging found that the tuatara had more of these genes than any other vertebrate species yet examined.

“Could this be one of the keys to their long lifespan?” Tuatara don’t seem to get many diseases either, so examining what genetic factors might protect them from infection was another focus of our study,” says Neil Gemmell, professor and team leader at the University of Otago.

A vulnerable icon

“The tuatara is an emblematic species, both for Maori and for biologists. It has a unique biology and its basic body shape hasn’t changed much during evolution, so it’s a valuable species for us to understand what the common ancestor of lizards, snakes and tuatara looked like. », explains Paul Flicek, associate director of Services EMBL-EBI.

Scientists hope their findings about the tuatara’s genome and biology will inform conservation efforts to protect this unusual reptile. The Tuatara thrived in New Zealand before the first human settlers introduced invasive predators such as rats 800 years ago. The extremely slow life cycle of the tuatara is no match for the voracity of its predators: when it comes to reproduction, the tuatara take the tourist route. It sometimes takes them more than 10 years to reach sexual maturity and they only produce young every two to five years. Although the species’ conservation status is ‘least concern’ according to the IUCN Red List of Threatened Species, the tuatara relies on active conservation management to prevent the establishment of invasive species. on the islands where it survives.

“Early on, it became clear that one of our main goals was to develop new knowledge that would improve the conservation of this species. We have agreed to partner with Ngātiwai to achieve this goal, while seeking opportunities to share other benefits that may arise from the research. It was an informed partnership that I believe has been an important enabler to the success of the project, which extends far beyond the scientific achievement of genome sequencing,” says Gemmell.

Reference: “The tuatara genome reveals ancient features of amniote evolution” by Neil J. Gemmell, Kim Rutherford, Stefan Prost, Marc Tollis, David Winter, J. Robert Macey, David L. Adelson, Alexander Suh, Terry Bertozzi, José H. Grau, Chris Organ, Paul P. Gardner, Matthieu Muffato, Mateus Patricio, Konstantinos Billis, Fergal J. Martin, Paul Flicek, Bent Petersen, Lin Kang, Pawel Michalak, Thomas R. Buckley, Melissa Wilson, Yuanyuan Cheng, Hilary Miller, Ryan K. Schott, Melissa D. Jordan, Richard D. Newcomb, José Ignacio Arroyo, Nicole Valenzuela, Tim A. Hore, Jaime Renart, Valentina Peona, Claire R. Peart, Vera M. Warmuth, Lu Zeng , R. Daniel Kortschak, Joy M. Raison, Valeria Velásquez Zapata, Zhiqiang Wu, Didac Santesmasses, Marco Mariotti, Roderic Guigó, Shawn M. Rupp, Victoria G. Twort, Nicolas Dussex, Helen Taylor, Hideaki Abe, Donna M. Bond , James M. Paterson , Daniel G. Mulcahy, Vanessa L. Gonzalez, Charles G. Barbieri, Dustin P. DeMeo, Stephan Pabinger, Tracey Van Stijn, Shannon Clarke, Oliver Ryder, Scott V. Edwards, Steven L. Salzberg, Lindsay Anderson, Nicola Nelson, Clive Stone and Ngatiwai Trust Board, August 5, 2020, Nature.
DOI: 10.1038/s41586-020-2561-9

This work was co-funded by the Wellcome Trust.

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