Wednesday, July 9, 2008

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

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!)

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