Biodiversity of New Zealand
The biodiversity of New Zealand, a large island country located in the south-western Pacific Ocean, is varied and distinctive.
New Zealand's pre-human biodiversity exhibited high levels of species endemism, but has experienced episodes of biological turnover.
Global extinction approximately 65 Ma (million years ago) resulted in the loss of fauna such as non-avian dinosaurs, pterosaurs and marine reptiles e.g. mosasaurs, elasmosaurs and plesiosaurs.
[citation needed] However geological evidence does not rule out the possibility that it was entirely submerged, or at least restricted to small islands.
Recent molecular evidence has shown that even the iconic Gondwanan plants the southern beeches (Nothofagus) arrived in New Zealand after separation of Zealandia from Gondwana.
The Miocene St Bathans fauna also preserves remains of a vesper bat and several incertae sedis species.
It is uncertain if many birds in New Zealand are descended from Gondwanan stock, as DNA evidence suggests that even the ratites (the kiwis and the moas) arrived after the split from Antarctica.
It appears that human hunters exterminated the moa populations, which deprived the Haast's eagle of its primary food source, leading to the extinction of that species as well.
New Zealand's emblematic kiwis fill the role of small foragers of the leaf-litter, and the enigmatic adzebill was a universal omnivore.
No agamas or iguanas are recorded from New Zealand; lizards are represented by geckos and skinks, which arrived multiple times.
The fossil record shows a highly diverse herpetofauna during the Miocene, with a mekosuchine crocodile and meiolaniid and pleurodire turtles being known from the St Bathans fauna.
The tuatara, reaching 60 cm (23.6 inches), is New Zealand's largest living reptile, a last remnant from the once diverse clade that was Sphenodontia.
The most famous of New Zealand's insects, the wētā, are ground-living relatives of the crickets that often reach enormous proportions.
The arrival of humans has impacted the natural environment, posing a threat to native species and resulting in the extinction of several.
This is predominantly because many species in New Zealand have evolved in the absence of mammalian predators for the last few million years (a situation known as ecological naivety), thus losing the responses needed to deal with such threats.
[22] Their arrival set off a first wave of extinctions, eliminating smaller defenceless ground nesting birds such as the New Zealand owlet-nightjar.
A second wave of extinctions was triggered by the arrival of the Māori, who hunted many of the larger species, such as the moa, adzebill and several large ducks and geese, for food.
A third wave of extinction began with the arrival of European settlers, who brought with them numerous new mammal species, particularly the predatory domestic cat, and initiated more habitat modification.
