DIVERSITY & ENDEMISM
New Caledonia is one of the world's smallest hotspots, yet it is very diverse and, like the other remnants of the ancient super-continent Gondwanaland (Madagascar, Australia, and New Zealand), supports high levels of endemism. This rich biodiversity and high endemism are due to its long-isolated evolution, as well as the variety of precipitation levels and very particular ultrabasic soils that cover more than one third of the country.
Endemism is especially high among vascular plants. There are about 3,270 plant species recorded on the islands, 74 percent of which are endemic (roughly 2,430 species). There are also 108 endemic genera, and a remarkable five endemic plant families: Amborellaceae, Paracryphiaceae, Strasburgeriaceae, Oncothecaceae, and Phellinaceae. Among countries, only Australia, South Africa, and Madagascar have more endemic plant families; these nations are also vastly larger than New Caledonia. Given this remarkable floristic endemism, New Caledonia is often considered a distinct floristic subkingdom.
Around 2,012 plant species are found in the evergreen rainforest, of which 82.2 percent are endemic, making it the richest of New Caledonia's vegetation types. Some 456 plant species have been recorded from the seclerophyllous forest type (57.5 percent endemic). Around 200 plant species occur in high-altitude maquis, of which 91 percent are endemic, and 1,144 plant species occur in the low- to mid-altitude maquis (89 percent endemic).
Exceptional plant groups found in New Caledonia include 44 species of gymnosperms, of which all but one species are endemic, including 13 endemic species of the genus Araucaria, an ancient group of Gondwanaland gymnosperms, of which there are only 19 worldwide, and the world's only parasitic conifer, Parasitaxus ustus. The territory also has 37 endemic species of palms, representing 16 endemic genera out of a total of 17. Furthermore, New Caledonia is home to the endemic, monotypic family Amborellaceae, which comprises a single species, Amborella trichopoda, recently shown to represent the basal-most branch in the evolutionary tree of the flowering plants.
Out of more than 100 birds found in New Caledonia, more than 20 are endemic. There are three endemic genera, two of which are monotypic, including the kagu (Rhynochetos jubatus, EN), the only living member of the endemic family, Rhynochetidae. Forest destruction and feral dogs gravely threaten the kagu, and only a few hundred individuals survive. Other distinctive bird species include the endemic New Caledonia imperial-pigeon (Ducula goliath), which is the world's largest arboreal pigeon, the endemic cloven-feathered dove (Drepanoptila holosericea), the New Caledonian owlet-nightjar (Aegotheles savesi, CR) known from only a few specimens, and most recently from an individual seen in 1998 in the Ni Riviere Valley. Two species from Caledonia that have not been recorded reliably for many years, include the New Caledonian lorikeet (Charmosyna diadema, CR), last recorded in 1913, and the New Caledonia rail (Gallirallus lafresnayanus, CR), not reliably reported since the early 20th century. New Caledonia is considered an urgent priority Endemic Bird Area (EBA) by Birdlife International.
All of New Caledonia's nine land mammal species are bats; five Microchiropters and four Megachiropters or flying foxes. Six of these bat species are endemic, including a newly described species of long-eared bat (Nyctophilus nebulosus) discovered in 1991 around Nouméa and caught for the second time in the same area in 2000. Bats have been poorly studied and the potential for discovering new species is high. Sadly, Megachiropters are highly threatened due to hunting. These species play a major role in dispersing the seeds of many rain forest tree species; when not hunted, they can develop large populations.
There is an extremely high level of reptile endemism in this hotspot. More than 60 of about 70 terrestrial reptiles are endemic, as are 11 of 23 genera. Nearly all of these species are lizards in two families of geckos and one family of skinks. The best known among these are the giant geckos of the endemic genus Rhacodactylus. Rhacodactylus leachianus, the largest gecko in the world, can grow up to 28 centimeters long, and weigh up to 700 grams. Phoboscincus bocourti, a 50-cm-long lizard, was previously known from a single specimen captured around 1870 and was long presumed extinct. In 2003, on a tiny islet, Phoboscincus bocourti was rediscovered.
The hotspot's two snake species, the Pacific boa (Candoia bibroni) and a small burrowing blind snake (Ramphotyphlops willeyi) from the family Typhlopidae, are restricted to the Loyalty Islands.
There are no native amphibians on New Caledonia.
Aquatic diversity on the islands is high given the size of the hotspot, with about 85 species of freshwater fish, although less than 10 are endemic. The most notable species is perhaps the endemic galaxiid Galaxias neocaledonicus, the northernmost representative of a group that is mostly restricted to the southern tips of New Zealand, Australia, South America, and Africa. A single genus, Protogobius, is endemic.
Among invertebrates, the hotspot supports a rich endemic diversity of land snails, although only 200 species have been described out of an estimated 400 to 600 species. The largest of these snails, Placostylus fibratus, can grow to more than 15 centimeters long and weigh up to 100 grams.
The hotspot has an estimated 37 species of macro-crustaceans, of which 40 percent are endemic. Grande Terre island is one of the most biodiverse islands for this taxonomic group, with species found only in ultrabasic substrata and others only in some short, oxygenated rivers of the north. Some gravely restricted species are highly threatened by nickel mining.
About 4,000 insect species have been catalogued to date, showing high endemism at the species and genus levels. The total insect fauna in the hotspot is projected to be between 8,000 and 20,000 species, including more than 70 native species of butterfly, more than 300 species of moth, and 16 tiger beetles. Nearly 200 spiders have been recognized thus far, including the only family of spiders endemic to a single island, the Bradystichidae.