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Glaciations drove kiwi diversity

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Kiwi are more diverse than previously realised, thanks to ice age glaciations driving evolution into multiple lineages. Canadian researchers, in collaboration with Department of Conservation scientists, examined a database of kiwi DNA across the geographic range of the five known kiwi species. They found the five kiwi species divided into 11 distinct lineages, as well as another five or six extinct lineages. The majority of diversification happened during the Middle and Late Pleistocene when there were major glacial advances, about 800,000 to 11,000 years ago. The authors suggest advancing glaciers drove kiwi into small refugia before expanding again as the glaciers retreated.

Journal/conference: PNAS

Organisation/s: University of Toronto, Canada

Funder: Funding for the study came from the Natural Sciences and Engineering Research Council of Canada and the University of Toronto Scarborough.

Media Release

From: University of Toronto

Innovative DNA testing shows New Zealand’s national symbol is the newer bird on the block

New Zealand’s kiwi may be one of the world’s oddest birds – flightless, nocturnal, an enigmatic dirt digger with nostrils at the end of its long bill. But the national symbol also has a lot to tell the world about evolution during the most recent ice age.

According to research published in the prestigious U.S. journal Proceedings of the National Academy of Sciences by a team led by Jason Weir, biological sciences professor at the University of Toronto Scarborough, today’s kiwi are much newer birds – genetically speaking – than previously thought. And instead of five known species, Weir says there are 11 types – either species or subspecies – alive now, with another six extinct.

Earlier research, based on simple methods of DNA testing using a single genetic marker, appeared to show that kiwi had developed into various species before the Pleistocene ice age that began some 2.6 million years ago and ended about 11,000 years ago. Many other creatures around the world had been classed the same way using similar methods.

But by deploying new and far more sophisticated DNA testing which tracks thousands of genetic markers on the kiwi genome, Weir’s research shows kiwi underwent an “explosive” period of genetic diversification – evolving into new species or subspecies – during the middle and late Pleistocene period.

As ice spread over the land, particularly on New Zealand’s South Island, kiwi retreated to isolated refuges where they gradually evolved new characteristics over the course of tens of thousands of years. This pattern was repeated continually as the ice expanded and shrank some seven times over a period of nearly 800,000 years.

Weir found that the rate of diversification increased five-fold during the glaciation period, to a level even greater than Charles Darwin’s famous finches from the Galapagos Islands.

Weir is among the first to use the new DNA techniques to measure evolutionary changes. “These new methods are going to be used extensively in the next 10 years,” he says. He expects scientists to revisit evolutionary studies of many birds and animals in North and South America and other parts of the world that had periods of glaciation. “The old system is out the window now.”

Weir and researcher Oliver Haddrath of the Royal Ontario Museum (ROM) carried out the massive task of analyzing the genetic data was carried out on Canada’s SciNet supercomputer. Some 300 samples of kiwi blood were collected by two New Zealand collaborators and by Allan Baker, a New Zealander by birth who was senior curator of ornithology and head of the Department of Natural History at the ROM before he died in 2014. The team also used previously published data from fossilized kiwi material.

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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.

Dr Kirstina Ramstad, Assistant Professor, University of South Carolina Aiken

Weir et al have provided one of the first really powerful genomics papers on kiwi, where they’ve used thousands of loci throughout the kiwi genome to properly characterisation the number of genetically distinct taxa. This is critical to understanding the role of glaciation in kiwi diversification but is also key to current kiwi management.

There have been 5 species containing 11 differentiated regional groupings recognised in kiwi for some time now. But that was based on extremely limited data and needed further testing. This study provides the first really strong evidence of which groups of kiwi should be managed separately by DOC.

The study also uses some of the latest bioinformatics techniques to estimate timing among kiwi species, updating divergence times from 4 to 16 million years ago and predated glaciation, to 0.6 to 1.6 million years and coinciding with the major glacial cycles of the Pleistocene.
 
This is really interesting and important work – it strongly supports DOC's current management scheme and shows rather fast adaptive radiation among birds that rarely do anything quickly!

Last updated: 03 Nov 2016 6:56pm
Associate Professor Jason Weir, Department of Ecology and Evolution, University of Toronto

Our research has important conservation implications for New Zealand. In the early 1990s only three species of kiwi were recognised. Genetic work by my key collaborator Allan Baker extended this number to five species.

Our work here built on these earlier studies but included a lot more individuals from throughout each species geographic range. Unlike earlier studies which relied on genetic evidence from a single genetic marker, our study used a genome-wide perspective by including approximately 6000 genetic markers.

The key finding was a clear genetic signature that 11 distinct kiwi lineages were involved (as well as several additional extinct ones). While we do not yet know if these lineages represent distinct species, they do represent genetically unique sets of populations which require management as separate conservation units.

This has great impact on management decisions. Already, the Department of Conservation has leaned heavily on the findings of our work to decide whether or not birds from certain populations can be bred together as they seek to introduce new populations, or augment the numbers of natural populations.

Last updated: 03 Nov 2016 5:09pm
Dr Lara Shepherd, Research Fellow at Te Papa.

This new publication provides the most in-depth study to date into the genetic relationships within kiwi. By examining DNA sequences from kiwi across New Zealand, including from areas where kiwi are now extinct, the authors were able to show that there are 16 to 17 distinct genetic lineages of kiwi (5-6 of these are extinct), far more than the five species currently recognised.

This new knowledge will help prevent the loss of any more distinct kiwi lineages by assisting the Department of Conservation to set priorities for kiwi conservation.

This study highlights how much we still have to learn about New Zealand's animals and plants. If we are still finding new types of kiwi, one of our most iconic and well-funded birds, then how much of the diversity are we overlooking in under-studied groups such as invertebrates, fungi and liverworts?

Last updated: 03 Nov 2016 4:25pm

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