DIVERSITY & ENDEMISM
As is true of the other fragments of Gondwanaland – Madagascar, Australia, and New Caledonia – New Zealand has remarkable levels of endemism among plants, birds, and reptiles.
Plant endemism is very high in New Zealand. Nearly 1,900 of about 3,400 species of vascular plants are endemic. Endemism also extends to the genus level; 35 plant genera are found nowhere else in the world. An example is the endemic monotypic genus Desmoschoenus spiralis or Pingao golden sand sedge, a coastal plant used by the Maori people in traditional building construction.
The fern Loxoma cunninghamii is one of the hotspot's "living fossils." Together with three species from Central America, L. cunninghamii constitutes the family Loxomataceae, whose closest relatives existed 60 million years ago. The hotspot also has one endemic family, the Ixerbaceae, which is represented by a single species (Ixerba brexiodes).
Nearly 200 bird species regularly occur in New Zealand, almost 90 of which (44 percent) are endemic. Not surprisingly, five Endemic Bird Areas identified by BirdLife International occupy nearly the entire area of the country. The hotspot also has 17 endemic bird genera and three endemic bird families, Acanthisittidae, Apterygidae, and Callaeidae. Moreover, it is the only hotspot to have an endemic bird Order, represented by the endearing, flightless kiwis (Apterygiformes), also the national bird of New Zealand.
Unfortunately, New Zealand's existing bird diversity represents only a fraction of the birds that once occupied the island. The hotspot has suffered 20 bird extinctions since 1500, including Stephens Island wren (Traversia lyalli), the only case in which an entire species was rendered extinct by the predatory instincts of a single introduced cat. Other historically extinct species include the giant flightless moas, which could grow to more than 3.5 meters in height, the bizarre flightless adzebill (Aptornis), which weighed up to 10 kilograms and bears no resemblance to any other known bird, and the largest eagle in the world, Haast's eagle (Harpagornis moorei), which preyed on moa.
A recent staggering development was the 2003 rediscovery of the New Zealand storm petrel (Oceanites maorianus, CR) in waters just off North Island. The 2003 sightings were the first records of this species, which had previously been known only from fossil material and three nineteenth-century specimens.
A number of other species are highly threatened today, including the kakapo (Strigops habroptilus, CR), a large, nocturnal, flightless parrot, which has suffered habitat destruction and extensive predation by introduced species like stoats and dogs. By 1976, the known population was 18 birds, all males, and all in Fiordland. In 1977, a rapidly declining population was discovered on Stewart Island, and so between 1980 and 1992 some 60 surviving birds were translocated to offshore islands, and currently survive on Maud, Inner Chetwode, Codfish, and Pearl Islands. In 1999, the population numbered 26 males and 36 females, with 50 animals of reproductive age. The population has since stabilized and is increasing.
All four species of kiwi are also threatened: tokoeka (Apteryx australis, VU), great spotted kiwi (Apteryx haastii, VU), brown kiwi (Apteryx mantelli, EN), and little spotted kiwi (Apertyx owenii, VU). These unusual birds are much smaller cousins of ostriches, emus, and rheas. Kiwis are mammal-like birds, with hairy feathers, sensory whiskers, an acute sense of smell, and short, squat bodies. They have marrow-filled bones (rather than hollow bones like other birds) and lay an egg that is 25 percent of their own body weight, which incubates for 2-3 months before hatching.
Finally, New Zealand also has the most diverse seabird community in the world, with around 80 species known to breed here. At least three-quarters of the world's penguin species breed in the New Zealand region, including the threatened endemic yellow-eyed penguin (Megadyptes antipodes, EN).
Both land mammal species native to the hotspot are endemic bats, one of which is the only living representative of the endemic bat family Mystacinidae: the New Zealand lesser short-tailed bat (Mysticina tuberculata, VU). This bat species is an oddity in that it walks about on all fours on the ground in predator-free environments. Its relative, the greater short-tailed bat (Mystacina robusta) is Extinct. The second land mammal species found in New Zealand is the long-tailed wattled bat (Chalinolobus tuberculatus, VU), which has suffered significant population declines recently. THe Hooker's sea lion (Phocarctos hookeri, VU) also occurs in this hotspot.
Nearly 40 species of reptiles are found in New Zealand, and all are unique to the islands; the fauna comprises geckos and skinks only, and there are no native snake species. In addition, a remarkable five of six reptile genera are endemic to the hotspot. The region also boasts an entire endemic order, the tuataras (Order Rhynchocephalia). The tuataras resemble iguanas and are primitive species that have existed since the dinosaur age, famous for their well-developed third eye. Although tuataras once ranged throughout much of the hotspot, the arrival of the Polynesia rat (Rattus exulans) greatly reduced their numbers. Two remaining species, Sphenodon punctatus and S. guntheri, are confined to 30 predator-free offshore islands where the New Zealand Department of Conservation is hoping the species' small populations will rebound.
Amphibians are represented in New Zealand by just four primitive frog species of the endemic family Leiopelmatidae. All four species are threatened, among them Archey's frog (Leiopelma archeyi, CR), which occurs on North Island in the Whareorino range in the west and Coromandel ranges in east, and has been severely affected by chytrid fungus.
Of the nearly 40 freshwater fish species native to New Zealand, about 25 (64 percent) are found nowhere else. The fish fauna is dominated by members of the family Galaxiidae, a group of coolwater trout-like fishes restricted to the southern tips of South America, Africa, Australia and New Zealand. Nearly 20 of the more than 50 galaxiid species known worldwide are found in New Zealand, and all but a few are endemic to the hotspot.
Additional research on New Zealand's invertebrate fauna is needed. The hotspot is home to 28 species of gastropods for which IUCN Red List assessments are available, six of which are considered to be Data Deficient by the IUCN Red List. Two species of land snail are threatened, Rhytida clarki (CR) and R. oconnori (CR), and a further three species of flax snails may soon be (Placosylus ambagiosus (VU), P. bollonis (VU), P. hongii(VU)). Six species are recorded as being Extinct, all from Norfolk Island.
A distinctive element of the New Zealand biota is the widespread occurrence of gigantism. Although some of the giant forms include the now extinct flightless moas and Haast's eagle, this element is still noticeable in some giant insects, myriapods, flatworms, land snails, centipedes, slugs, and earthworms. The world's heaviest insect, the weta or wingless cricket of Little Barrier Island (Hauturu) weighs up to 70 grams and is one of 12 species of Deinacrida, the ancestors of which roamed the Jurassic forests.