DNA study says there may be 11 kiwi species, ancestors driven apart by glaciers
Tuesday, 30 August 2016
Kiwi are weird.
The bumbling flightless birds have long snouts with nostrils at the tip, they're nocturnal, and they smell a bit like mushrooms.
Now, a groundbreaking DNA study of more than 200 birds suggests there are more species than the recognised five types and 16, or 17, distinct genetic forebears.
At least five, possibly six, of these genetic lineages are extinct species, the study says.
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Research published in the the Proceedings of the National Academy of the Sciences by the University of Toronto on kiwi DNA says the modern birds - genetically speaking - evolved more recently than previously thought.
A team led by University of Toronto Scarborough professor of biological sciences Jason Weir discovered that instead of the five known species, there are 11 types of birds alive now, with six species extinct.
Scientists in Canada worked alongside the Department of Conservation.
They have not concluded whether the 11 types represent separate species, or subspecies, but the lineages do represent separate populations.
'In the early 1990s only three species of kiwi were recognised. Genetic work by [New Zealander] 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,' Weir said.
Scientists think the different species evolved during a period of extreme glaciation, when the birds were cut off by advancing and retreating glaciers and ice sheets.
Earlier research appeared to show kiwi developed into different species before the Pleistocene ice age, which spanned eons from around 2.6 million years ago to 11,000 years ago.
Weir's DNA technique shows kiwi species experienced explosive genetic variation, evolving into species or subspecies, during the Pleistocene.
As ice caps and glaciers spread across New Zealand, the birds retreated to isolated regions where they evolved new characteristics and features over tens of thousands of year. As glaciers advanced and retreated these patterns of evolution repeated at least seven times over 800,000 years, the research says.
The study has implications for diversifying the conservation methods for kiwi management.
Te Papa research fellow Dr Lara Shepherd said the study was - so far - the most in-depth look at the genetic evolution of 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, far more than the five species currently recognised.
'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?'
The Department of Conservation estimates the kiwi population at 68,000. The closest living relative is the elephant bird of Madagascar and the birds are also related to emus, cassowaries and the extinct New Zealand moa.
All five species - the brown kiwi, the great spotted kiwi, the little spotted kiwi, rowi, and tokoeka - are classed as threatened or at risk.