The first thought that comes to mind when the word evolution is mentioned is either Darwin, his finches, or humans and apes. But for me the kea, kaka and proto-kaka are among my first thoughts. I went to university in New Zealand, and where possible, our lecturers subsequently liked to use New Zealand examples. And so this brings me to mention a paper I did in evolution, from which one of the things that stood out to me most was the relationship between these parrots.

The kea and kaka share a common ancestor, named the proto-kaka, from which they both evolved. The speciation of the kea is thought to have begun to occur around 2-3 million years ago as a result of the gradual uplift of the Southern Alps, which began around 5 million years ago (during the Pliocene). Along with this new developing environment new ecological niches arose, of which the kea took advantage. The result was that the kea evolved to be able to survive in such a harsh environment, and has consequently become the world’s only alpine parrot.

However the evolutionary history of these guys does not stop there. Around 2.6 million years ago the Pleistoscene began, this is marked by the beginning of the the last ice-age, a period of glaciation. As a result of glaciation the sea levels decreased enough that the North and South Islands of New Zealand became one for a time, creating a land-bridge between them. Kaka were pushed north due to the increased ice and cold in the south which had decreased their natural habitat area. When the ice retreated, around 12,000 years ago, the sea levels rose again, separating two major populations of kaka along with the North and South Islands. This has given rise to the two extant sub-species of kaka. They are still only a sub-species as significant time has not yet passed for them to evolve into two separate species. However eventually they will, if the barriers preventing the two populations from inter-breeding remain in place.

Going back even further in time, DNA studies suggest that around 60-80 million years ago the proto-kaka and kakapo (another unique New Zealand parrot), diverged from their common ancestor (the proto-kaka/kakapo). It is thought this occurred through ecological separation: two populations of their ancestor moved into different ecological niches causing reproductive isolation between the groups, hence eventually evolution of the two separate species.

And if you wanted to go back even further the ancestor of the proto-kaka/kakapo is thought to have been Australian. This ancestor evolved into the proto-kaka/kakapo when 100 million years ago Gondwanaland broke up, separating New Zealand from Australia.

This website, http://sci.waikato.ac.nz/evolution/index.shtml has some very interesting articles on a number of different aspects of evolution, including a section on New Zealand evolution.

References: http://sci.waikato.ac.nz/evolution/NZevidence.shtml, http://www.doc.govt.nz/upload/26539/North-island-kaka.pdf