New Zealand Parrot - Phylogeography

Phylogeography

A hypothesis for the phylogeography of this group has been proposed and this provides a nice example of various speciation mechanisms at work. In this scenario, ancestors of this group became isolated from the remaining parrots when New Zealand broke away from Gondwana about 82 million years ago, resulting in a physical separation of the two groups. This mechanism is called allopatric speciation. Over time, ancestors of the two surviving genera, Nestor and Strigops, adapted to different ecological niches. This led to reproductive isolation, an example of ecological speciation. In the Pliocene, around five million years ago, the formation of the Southern Alps diversified the landscape and provided new opportunities for speciation within the genus Nestor. Around three million years ago, two lineages adapted to high altitude and low altitude, respectively. The high altitude lineage gave rise to the modern Kea, while the low altitude lineage gave rise to the various Kākā species. Island species diverge rapidly from mainland species once a few vagrants arrive at a suitable island. Both the Norfolk Kākā as well as the Chatham Kākā are the result of migration of a limited number of individuals to islands and subsequent adaptation to the habitat of those islands. The lack of DNA material for the Chatham Kākā makes it difficult to establish precisely when those speciation events occurred. Finally, in recent times, the Kākā populations at the North Island and South Island became isolated from each other due to the rise in sea levels when the continental glaciers melted at the end of the Pleistocene.

Until modern times New Zealand and the surrounding Islands were not inhabited by four-legged mammals, an environment that enabled some birds to adapt to make nests on the ground and others to become flightless.

The parakeet species belonging to the genus Cyanoramphus (kākārikis) belong to the true parrot family Psittacidae and are closely related to the endemic genus Eunymphicus from New Caledonia. They reached New Zealand between 450,000 and 625,000 years ago from mainland Australia by way of New Caledonia.