Biodiversity of New Zealand

The biodiversity of New Zealand, a large Pacific archipelago, is one of the most unusual on Earth, due to its long isolation from other continental landmasses. Its affinities are derived in part from Gondwana, from which it separated 82 MYA, some modest affinities with New Caledonia and Lord Howe Island, both of which are part of the same continental plate as New Zealand and in part from Australia. More recently a component has been introduced by humans. New Zealand's biodiversity exhibits high levels of endemism, both in its flora and fauna. Until recently the islands had no native terrestrial mammals except for bats (although mammals did exist in New Zealand until 19 million years ago), the main component of the fauna being insects and birds. Its flora is dominated by Gondwanan plants, comprising historically of forests, most famously the giant kauri. New Zealand has developed a national Biodiversity Action Plan to address conservation of considerable numbers of threatened flora and fauna within New Zealand.

[edit] Evolution of New Zealand's biodiversity
The break up of the supercontinent of Gondwana left the resulting continents and microcontinents with shared biological affinities. New Zealand, along with New Caledonia, began to move away from Antarctic Gondwana 100 MYA, the break being complete by 82 MYA. It has been moving northwards since then, changing both in relief and climate. At some points it has been mostly underwater, with as little as 18% of the present surface area being above the water. Of the original biodiversity that it carried with it from Gondwana several groups remain: predominantly plants, such as the podocarps and the Southern beeches, but also a distinctive insect fauna, New Zealand's unusual frogs and the tuatara, as well as some of New Zealand's birds. It seems likely that some primitive mammals also were part of the original cargo.

The two sources of New Zealand's biodiversity following separation from Gondwana have been speciation and air- or sea-borne immigration. Most of these immigrants have arrived from Australia, and have provided the majority of New Zealand's birds and bats as well as some plant species (carried on the wind or inside the guts of birds). Some of these immigrants arrived long enough ago that their affinities to their Australian ancestors are uncertain; for example, the affinities of the unusual Short-tailed Bat were unknown until fossils from the Miocene were found in Australia. It has been suggested that the unusual adzebills are related to the Kagu of New Caledonia, and the Cyanoramphus parakeets are thought to have originated in New Caledonia. The link between the two island groups also includes affinities between skink and gecko families.


[edit] Elements of New Zealand's Biodiversity

[edit] Floral biodiversity

The kauri of North Island were the tallest trees in New Zealand, but were extensively logged and are much less common today.The history, climate and geology of New Zealand have created a great deal of diversity in New Zealand's vegetation types. The main two types of forest have been dominated by podocarps and southern beech. Podocarps (Podocarpaceae), an ancient evergreen gymnosperm family of trees, have changed little in the last 190 million years. Forests dominated by podocarps form a closed canopy with an understory of hardwoods and shrubs. The forests of southern beeches, from the genus Nothofagus, comprise a less diverse habitat, with the beeches of four species dominating the canopy and allowing a single understory. In the north of New Zealand the podocarp forests were dominated by the ancient giant kauri. These trees are amongst the largest in the world, holding the record for the greatest timber volume of any tree. The value of this was not lost on early European settlers, and most of these trees were felled.

The remaining vegetation types in New Zealand are grassland of grass and tussock, usually associated with the subalpine areas, and the low shrublands between grasslands and forests. These shrublands are dominated by daisies, which can become woody and 3 m high.


[edit] Faunal diversity
Until 2006 it was thought that no mammals, other than bats and marine mammals, had reached New Zealand before humans did. The discovery of a femur and mandibles of an extinct non-volant mammal in Otago, dated at 16-19 million years old, has changed the view of New Zealand's evolutionary history, as it strongly suggests that mammals had been part of New Zealand's fauna since the break-up of Gondwana. The fossil has been called SB mammal. It is not known when, or why, land mammals went extinct in New Zealand but there were none present on new Zealand for several million years before the arrival of man.

The Short-tailed Bat (from the monotypic family Mystacinidae), having arrived in the late Oligocene, has had plenty of time to evolve, and has begun to fill the role of a small terrestrial mammal, flying out from roosts at night but frequently foraging on the ground. Some plants have evolved with the bats and are fertilised on the ground by the bats. The Long-tailed Bat (Chalinolobus tuberculatus), a more recent arrival, is relatively common.

Birds comprise the most important part of New Zealand's vertebrate fauna. 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 moa) arrived after the split from Antarctica. Recent studies suggest that New Zealand wrens are Gondwanan descendants. DNA studies seem to indicate that the wrens are the most ancient of all passerines, splitting from the ancestral passerine stock at the time New Zealand become an isolated land mass. In the absence of mammals, birds diversified into the niches usually filled by mammals in other ecosystems.


The extinct Huia was a member of the endemic family Callaeidae.The moa, of which there were 10 species, were large browsers, and were in turn the prey species of the giant Harpagornis Eagle or Haast's Eagle. Both moa and eagles became extinct shortly after the arrival of humans to New Zealand sometime around 1300 CE. It appears that human hunters exterminated the moa populations, which deprived the Harpagornis of their primary food source, leading to the extinction of that species, as well. New Zealand's emblematic kiwi fills the role of a small forager of the leaf-litter, and the enigmatic adzebill was a universal omnivore. The wattlebirds, Callaeidae, are a family endemic to New Zealand, but many other New Zealand birds show clear affinities to Australia, including the New Zealand Pigeon and the New Zealand Falcon, as well as various parrots, rails, waders, owls, and seabirds (albeit often with a New Zealand twist). Of the 245 species of birds from the greater New Zealand (the main islands along with the offshore islands, also including Norfolk Island), 174 were endemic, roughly 71%. Of these, about 32% of the genera were endemic.


The tuatara is a unique component of New Zealand's biodiversity and the only surviving genus in the order Sphenodontia.No agamas, iguanas, land turtles or snakes are recorded from New Zealand. The fossil record shows one crocodile, possibly a mekosuchine crocodile, in the Miocene, but otherwise the only reptiles to reach New Zealand were skinks, geckos, and the tuatara, a living fossil. The tuatara, reaching 60 cm, are New Zealand's largest reptiles. Frogs, which because of their intolerance for saltwater are assumed to have descended from ancestors that broke off from Gondwana, are one of the few exceptions to the rule that amphibians are never found on oceanic islands (another being the frogs of Fiji). New Zealand's few wholly freshwater fishes are derived from diadromous species.

New Zealand's invertebrate community displays strong Gondwanan affinities, and has also diversified strongly, if unevenly. There are over a thousand species of snail, and many species of insect have become large and in many cases flightless, especially grasshoppers and beetles. There are, however, less than 12 species of ant. The most famous of New Zealand's insects, the wetas, are ground-living relatives of the crickets that often reach enormous proportions.

[edit] Evolution of New Zealand's biodiversity
The break up of the supercontinent of Gondwana left the resulting continents and microcontinents with shared biological affinities. New Zealand, along with New Caledonia, began to move away from Antarctic Gondwana 100 MYA, the break being complete by 82 MYA. It has been moving northwards since then, changing both in relief and climate. At some points it has been mostly underwater, with as little as 18% of the present surface area being above the water. Of the original biodiversity that it carried with it from Gondwana several groups remain: predominantly plants, such as the podocarps and the Southern beeches, but also a distinctive insect fauna, New Zealand's unusual frogs and the tuatara, as well as some of New Zealand's birds. It seems likely that some primitive mammals also were part of the original cargo.

The two sources of New Zealand's biodiversity following separation from Gondwana have been speciation and air- or sea-borne immigration. Most of these immigrants have arrived from Australia, and have provided the majority of New Zealand's birds and bats as well as some plant species (carried on the wind or inside the guts of birds). Some of these immigrants arrived long enough ago that their affinities to their Australian ancestors are uncertain; for example, the affinities of the unusual Short-tailed Bat were unknown until fossils from the Miocene were found in Australia. It has been suggested that the unusual adzebills are related to the Kagu of New Caledonia, and the Cyanoramphus parakeets are thought to have originated in New Caledonia. The link between the two island groups also includes affinities between skink and gecko families.


[edit] Elements of New Zealand's Biodiversity

[edit] Floral biodiversity

The kauri of North Island were the tallest trees in New Zealand, but were extensively logged and are much less common today.The history, climate and geology of New Zealand have created a great deal of diversity in New Zealand's vegetation types. The main two types of forest have been dominated by podocarps and southern beech. Podocarps (Podocarpaceae), an ancient evergreen gymnosperm family of trees, have changed little in the last 190 million years. Forests dominated by podocarps form a closed canopy with an understory of hardwoods and shrubs. The forests of southern beeches, from the genus Nothofagus, comprise a less diverse habitat, with the beeches of four species dominating the canopy and allowing a single understory. In the north of New Zealand the podocarp forests were dominated by the ancient giant kauri. These trees are amongst the largest in the world, holding the record for the greatest timber volume of any tree. The value of this was not lost on early European settlers, and most of these trees were felled.

The remaining vegetation types in New Zealand are grassland of grass and tussock, usually associated with the subalpine areas, and the low shrublands between grasslands and forests. These shrublands are dominated by daisies, which can become woody and 3 m high.


[edit] Faunal diversity
Until 2006 it was thought that no mammals, other than bats and marine mammals, had reached New Zealand before humans did. The discovery of a femur and mandibles of an extinct non-volant mammal in Otago, dated at 16-19 million years old, has changed the view of New Zealand's evolutionary history, as it strongly suggests that mammals had been part of New Zealand's fauna since the break-up of Gondwana. The fossil has been called SB mammal. It is not known when, or why, land mammals went extinct in New Zealand but there were none present on new Zealand for several million years before the arrival of man.

The Short-tailed Bat (from the monotypic family Mystacinidae), having arrived in the late Oligocene, has had plenty of time to evolve, and has begun to fill the role of a small terrestrial mammal, flying out from roosts at night but frequently foraging on the ground. Some plants have evolved with the bats and are fertilised on the ground by the bats. The Long-tailed Bat (Chalinolobus tuberculatus), a more recent arrival, is relatively common.

Birds comprise the most important part of New Zealand's vertebrate fauna. 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 moa) arrived after the split from Antarctica. Recent studies suggest that New Zealand wrens are Gondwanan descendants. DNA studies seem to indicate that the wrens are the most ancient of all passerines, splitting from the ancestral passerine stock at the time New Zealand become an isolated land mass. In the absence of mammals, birds diversified into the niches usually filled by mammals in other ecosystems.


The extinct Huia was a member of the endemic family Callaeidae.The moa, of which there were 10 species, were large browsers, and were in turn the prey species of the giant Harpagornis Eagle or Haast's Eagle. Both moa and eagles became extinct shortly after the arrival of humans to New Zealand sometime around 1300 CE. It appears that human hunters exterminated the moa populations, which deprived the Harpagornis of their primary food source, leading to the extinction of that species, as well. New Zealand's emblematic kiwi fills the role of a small forager of the leaf-litter, and the enigmatic adzebill was a universal omnivore. The wattlebirds, Callaeidae, are a family endemic to New Zealand, but many other New Zealand birds show clear affinities to Australia, including the New Zealand Pigeon and the New Zealand Falcon, as well as various parrots, rails, waders, owls, and seabirds (albeit often with a New Zealand twist). Of the 245 species of birds from the greater New Zealand (the main islands along with the offshore islands, also including Norfolk Island), 174 were endemic, roughly 71%. Of these, about 32% of the genera were endemic.


The tuatara is a unique component of New Zealand's biodiversity and the only surviving genus in the order Sphenodontia.No agamas, iguanas, land turtles or snakes are recorded from New Zealand. The fossil record shows one crocodile, possibly a mekosuchine crocodile, in the Miocene, but otherwise the only reptiles to reach New Zealand were skinks, geckos, and the tuatara, a living fossil. The tuatara, reaching 60 cm, are New Zealand's largest reptiles. Frogs, which because of their intolerance for saltwater are assumed to have descended from ancestors that broke off from Gondwana, are one of the few exceptions to the rule that amphibians are never found on oceanic islands (another being the frogs of Fiji). New Zealand's few wholly freshwater fishes are derived from diadromous species.

New Zealand's invertebrate community displays strong Gondwanan affinities, and has also diversified strongly, if unevenly. There are over a thousand species of snail, and many species of insect have become large and in many cases flightless, especially grasshoppers and beetles. There are, however, less than 12 species of ant. The most famous of New Zealand's insects, the wetas, are ground-living relatives of the crickets that often reach enormous proportions.