Ghosts of Gondwana

How come New Zealand’s plants and animals are so different from those in the rest of the world, even nearby Australia? In Ghosts of Gondwana, Kiwi scientist George Gibbs sets out to provide some answers through historical biogeography – “the study of what lives where and why”.

Fortunately, one doesn’t have to be a scientist to understand the broad answers to how plants & animals got where and why they did. How plants and animals got to New Zealand is explained by current historical biogeography in terms of vicariance – they were on the tectonic plates that broke away to form New Zealand – they were in “Moa’s Ark”; dispersal – they arrived under their own power or caught a ride by air or water after the crustal plates separated; or by extinction – species survive in one place and not another for various reasons.

What sets New Zealand apart as “a completely different experiment in evolution”? What new niches were created by 60 plus million years of isolation? New Zealand’s endemic life (found nowhere else) is perhaps symbolized best in the modern mind by the flightless, nocturnal kiwi bird.

But there are also the tuatara, a long-lived reptile

the now extinct moa, shown here under attack by the extinct Haast's Eagle:

John Megahan

the weta, an insect among the largest and heaviest in the world

Less well-known, even among many New Zealanders, are the New Zealand Wrens – non-singing passerines (song birds) who at best can raise a tiny squeak – giant carnivorous land snails, and many insect species including the batfly and marine caddisflies.

Bush Wren - extinct in modern times

While not endemic, the stick insect is another one of New Zealand's oddities:

courtesy Landcare NZ

Just as revealing of the effects of geographic isolation are the species absent from New Zealand, despite many of them being present in nearest neighbour Australia: mammals, except native bats & seals, marsupials or monotremes (eg platypus), snakes, tortoises, scorpions, few butterfly families, and amongst the plants, cycads and horsetails. In the absence of mammals who might have acted as predators, many bird species evolved to be flightless and some also became nocturnal such as the kiwi and kakapo.

With the arrival of man, a number of introduced species including the kiore or Polynesian rat that arrived with the Maori and the Norway rat, the stoat and weasel, feral cat, and opossum that arrived with the European (pakeha) have severely reduced many endemic species, some to the point of extinction.

Gibbs’ summation of the current state of the scientific knowledge on New Zealand native species is that the evidence points to a mix of both ghosts of Gondwana, evolved species whose ancestors were separated by plate separation 60-80 million years ago and others that dispersed subsequently across the ocean barrier such as the kea, takahe, and pukeko.

George Gibbs, Ghosts of Gondwana, Craig Potton Publishing, is available at

www.craigpotton.co.nz

Note – This publisher provides exemplary international book sales service at a fair price. It's founder, a nature photographer, has produced superb work over the decades. But don't take my word for it, go check out the site. (And, no, I receive no benefit for saying so!)

Begin at the Beginning

Or at least at that point in deep time, some 60 to 80 million years ago (MYA), when what we now know as New Zealand broke away from Australia.

The science of plate tectonics suggests that the supercontinent of Gondwana formed around 170 million years ago and began splitting apart about 130 MYA as shown in the stylized map below. It was the southeastern region of Gondwana (diagonal lines) that acted as the platform for the evolution of life that would populate Australia & New Zealand.

Between 80 and 60 MYA, what would eventually become New Zealand began to drift away from that part of eastern Gondwana comprising Antarctica and Australia. The last piece to separate from New Zealand was New Caledonia which explains why the two have a number of species in common although evolution continued to take its divergent paths after separation.

from Gibbs, The Ghosts of Gondwana, 2006.

Isolated from the rest of the world’s land masses, life in New Zealand took its own distinctive path, leading scientists such as Jared Diamond to assert that “New Zealand is as close as we will get to the opportunity to study life on another planet” and Tim Flannery to call it “a completely different experiment in evolution from the rest of the world”.

Was this Moa’s Ark – a hermetically-sealed time capsule of life from Gondwana plus evolution over 60 million years – or was it also the result of later dispersals before man introduced new species?