By John Kerr 01/09/2016 2


Ancient walls of ice separating kiwi populations have left their mark in the DNA of New Zealand’s most iconic species.

A new study published this week in PNAS has revealed the enormous impact historic cold snaps had on the evolution of kiwis. Researchers based in Canada, 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.

Read more about the study on scimex.org.

Lead author Associate Professor Jason Weir, from the University of Toronto, told the Science Media Centre that the inclusion of more data in the new study revealed a clearer picture of kiwi evolution.

“Our work here built on 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,” he said.

When asked by tech site Motherboard if the findings hinted at the declaration of new kiwi species in the near future, Weir was only speculative. “Taxonomy is always highly controversial because people have different species concepts,” he said.

“Our paper’s going to add a little more fuel to that controversy.”

Evolutionary explosion during ice ages

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, which was marked by a number of ‘severe glacial periods’.

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.

Glacia
Distribution of glacial ice, bare rock, coastlines, and a likely scenario for the geographic distributions of 13 genetically differentiated lineages of the brown kiwi clade during the last glacial maximum (∼20,000 years ago), the early Holocene before human arrival, and at the present. From Weir et al., (2016) PNAS.

Important findings for kiwi conservation

“This has great impact on management decisions,” said Weir. “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.”

Kiwi chick. Image Credit: Department of Conservation.
Image Credit: Department of Conservation.

 

Kiwi researcher Dr Kristina Ramstad, from the University of South Carolina Aiken, agreed the finding were key to current kiwi management.

“This is really interesting and important work,” she said to the Science Media Centre. “It strongly supports DOC’s current management scheme. This study provides the first really strong evidence of which groups of kiwi should be managed separately by DOC.”

Massey University’s Isabel Castro explained the situation to Ed Yong at National Geographic:

These results have important implications for conserving kiwis, says Isabel Castro from Massey University in New Zealand. She and her colleagues were aware of some of these subspecies and were caring for them accordingly. “This study means we now we have conclusive support for obtaining funding, or dividing available funding, across all of the lineages,” she says. “And it tells us we need to concentrate on those species that we don’t know anything about, like those on South Island, and learn what we can to protect them.”

For example, the lineages might look very similar, but Weir suggests that they might differ in their calls and smells—traits that would affect their ability to find, recognize, and attract mates. Castro adds that her team has already found important differences in the kiwis’ bill-tip organs (which help them find food as they probe the leaf litter with their beaks) and their uropygial glands (which produce oils that affect their scents). It goes to show that you shouldn’t judge a kiwi by its cover.

Featured image: Flickr / Smithsonian’s National Zoo.


2 Responses to “Ice ages led to ‘explosive’ diversity in Kiwi species”

  • Your maps raise a few questions. You have Tasman rowi (southern brown) on your map during glaciation, with no mention of the Roa (great spotted Kiwi) which still resides there today with the assistance of the Paparoa Wildlife Trust. If you check with Forest & Bird, I’m sure there is still a healthy population of Kiwi in the Arthurs Pass and surrounding valleys which isn’t noted on your present map either

  • Well spotted Rosemary. That map (taken from the original research article) only considers the brown kiwi clade (Apteryx australis, rowi, & mantelli, I think), and doesn’t include great spotted kiwi (Apteryx haastii) although this species was included in researchers’ overall analysis. I think the Arthur’s Pass kiwi are great spotted kiwi, so that explains why they are not this particular map.