12/12/2011
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Extinct thrush gets makeover

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Despite appearances, the extinct Piopio is an oriole it seems. Image: J G Keulemens (commons.wikimedia.org).
Despite appearances, the extinct Piopio is an oriole it seems. Image: J G Keulemens (commons.wikimedia.org).

The New Zealand Thrush or Piopio was a passerine endemic to its eponymous island group, with two distinct subspecies on the North and South Islands, as is typical of so many New Zealand forms. both forms were last seen in the 1940s, and the species is now regarded as extinct.

Its morphology has suggested that it is part of the larger Corvoidea, represented by crows, birds-of-paradise and shrikes, though some affinities have also been suggested with the true thrushes Turdidae. It has often been placed in its own family Turnagridae.

New research has now been published, after three nuclear genes were sequenced, all strongly suggesting that the Piopios were actually part of the Oriolidae, the Old World orioles, a surprising outcome considering their physical appearance. This group is represented in Australasia by both the figbirds Sphecotheres and true orioles Oriolus. Its exact position in the evolutionary history of the family is more tenuous, but two of the genes indicate that it is basal to much of it, and the Piopio is probably the most far-reaching example of the early colonisation and radiation of the group in Australasia, and are sister to the figbirds.

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The team estimate that Piopio diverged about 20 million years ago, giving plenty of time for the physical discrepancies between the species and true orioles to have developed in isolation. It is therefore likely that the ancestors of Piopio colonised via the Tasman Sea, rather than being transported as New Zealand separated from the ancient continent Gondwanaland about 70 million years ago. the poisonous pitohuis of New Guinea are also closely related to the ancestor of all the Oriolidae.

Reference
Johansson, U S, Pasquet, E and Irestedt, M. 2011. The New Zealand Thrush: An Extinct Oriole. PLoS ONE 6: e24317.