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Kea Genetics Shaped by Climate, Not People

Genetic variation in New Zealand’s kea is the result of recolonisation of alpine areas since the last ice age 10,000 years ago, and not due to population decline as a result of human colonisation, as initially thought.

Until the 1970s these alpine parrots were considered a pest for attacking livestock, with some 150,000 birds killed in a government-sanctioned cull. The species is now protected, but the population of 5000 birds is now in decline due to introduced mammalian predators.

In research published in Molecular Ecology, University of Otago researchers have sampled genetic variation across the kea’s range, using advanced population history modelling to tease apart the impacts of glaciations and human impacts since the colonisation of New Zealand by Polynesians.

“We found that human impacts are not responsible for shaping the present-day population structure of kea, which is instead the result of recolonisation of the South Island by the kea at the end of the last ice age some 10,000 years ago,” says Dr Nicolas Dussex.

“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 ice receding at the end of the ice age, kea moved out of their habitat refuges to recolonise 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.

“Kea used to be everywhere,” says co-author Dr Bruce Robertson. “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.”

Dussex says that the findings 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.”