A new study published in the journal Molecular Ecology reveals the glacial and post-glacial history of the kea, Nestor notabilis.
A juvenile Kea, Nestor notabilis, perching on some rubble on the Franz Josef Glacier, New Zealand. Image credit: Markus Koljonen / CC BY-SA 3.0.
The kea is a strong-flying, large parrot – about 48 cm long and weighing 0.8-1 kg – widely distributed in the mountains of the South Island of New Zealand.
This bird has mostly olive-green plumage with a brilliant orange under its wings and has a large, narrow, curved, grey-brown upper beak.
The call is a long, loud, high-pitched descending cry which may be broken ‘kee-ee-aa-aa,’ or unbroken ‘keeeeeaaaa.’
The kea is renowned for its intelligence and curiosity. It can solve logical puzzles, such as pushing and pulling things in a certain order to get to food.
Between the 1860s and the 1970s, the kea was considered a pest for attacking livestock, with some 150,000 birds killed in a government sanctioned cull.
The species is now protected, but numbers less than 5,000 birds and is in decline due to introduced predators.
Study lead author Dr Nicolas Dussex from the University of Otago in Dunedin, New Zealand, and his colleagues aimed to determine whether the recent kea population decline played a role in the shaping of the current genetic variation.
They have found that the kea’s current genetic makeup is not the result of human-induced decline as was initially thought and is instead due to natural re-colonization of the alpine mountains following the last Ice-Age 10,000 years ago.
The scientists sampled genetic variation across the kea’s range, sampling genetic material from 473 kea along the Southern Alps.
They used advanced population history modeling to tease apart the impacts on the genetic structure of kea of glaciations and of human – impacts since the colonization of New Zealand by Polynesians.
An adult Kea flying in its natural environment near Queenstown, New Zealand. Image credit: Christian Mehlführer / CC BY 2.5.
“We found that human impacts are not responsible for shaping the present-day population structure of kea, which is instead the result of re-colonization of the South Island by the kea at the end of the last ice age some 10, 000 years ago,” Dr Dussex explained.
The researchers’ findings also make an important contribution to kea conservation.
“Kea populations do not need to be managed separately because this population structure is relatively recent on an evolutionary time-scale, thus allowing conservation managers to move birds between populations as part of any conservation attempts to reverse the kea’s ongoing decline,” Dr Dussex said.
Inferring past demography is a central question in evolutionary and conservation biology, but it is often challenging to identify the processes shaping the patterns of genetic variation in endangered species, as they have already lost a lot of variation.
“The genetic structure of populations and limited variation can reflect the natural effect of past geological or glacial events, as well as the artificial effects of human activity, such as culls,” Dr Dussex said.
“It is quite likely that the kea’s habitat was very different during the last glacial period between 2.5 million years to 10,000 years ago, with birds being restricted to smaller areas by permanent ice and snow.”
“With the end of the ice age and the ice receding, kea moved out of their habitat refuges to re-colonize the South Island of New Zealand. This, rather than the impacts of human activity, is the likely reason for the patterns seen in the kea’s genetic variation,” said senior author Dr Bruce Robertson, also from the University of Otago.
“Kea used to be everywhere, then the Ice Age limited them to ice-free refuges most likely at the top of the South Island. At the end of this cold period, kea were then able to expand into their previous habitat over a wider range and into the habitat they occupy today.”
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N Dussex et al. Postglacial expansion and not human influence best explains the population structure in the endangered kea (Nestor notabilis). Molecular Ecology, published online March 30, 2014; doi: 10.1111/mec.12729
