Fauna of New Caledonia - Flora

Flora

New Caledonia's vegetation is distinguished by the world's highest rate of endemism: 5 families, 107 genera and 3,380 species. Among these are Acacia spirorbis, Dracophyllum species, Drosera novae-caledoniae, Grevillea gillivrayi, Cycas circinalis, Neocallitropsis pancheri (Cupressaceae), Austrotaxus spicatus (Taxaceae) and Parasitaxus ustus (Podocarpaceae). Of the 44 species of Gymnosperm in the archipelago, 43 are endemic, including the unique parasite Gymnosperm (Falcatifolium taxoides). The palm trees include 37 endemic species belonging to 16 genera. For the endangered Pritchardiopsis jennencyi, one only adult specimen is known. Three of the most primitive genera of Araliaceae also occur.

Some New Caledonia plant communities are true living fossils. Flora contains many groups of plants that appear to be remnants of the Gondwanan flora in late Cretaceous - early Tertiary that once covered large parts of Australasia. The flora is exceedingly diverse, and includes a level of endemism, per square kilometre, seen almost nowhere else on Earth. Three quarters of native plant species on New Caledonia are endemic, but a quarter of those are "at risk" of decline or extinction. There are besides 454 species of marine macrophytes.

By contrast, several groups that are well represented in the rest of tropics have only a few species on the Archipelago, such as Melastomataceae with one specie, or are absent all together, e.g., Ochnaceae (sensu stricto) and Begoniaceae. Other families, such as Araceae, Boraginaceae, Brassicaceae, Commelinaceae, Gesneriaceae, and Zingiberaceae, are substantially under-represented.

Five families are considered endemic: the Amborellaceae, the Oncothecaceae, the Phellinaceae that was often included in Aquifoliaceae, the Paracryphiaceae, and the Strasburgeriaceae, before placed in Ochnaceae.

Some genera originated in the Gondwanian Antarctic flora. The most remarkable Gondwanian groups include the Cunoniaceae, the Myrtaceae, the Escalloniaceae and the Proteaceae. Due to this fact, the islands share many plant families with the Valdivian forest of South America, New Zealand, Tasmania and Australia, in habitats of cloud forest and temperate rainforest. Angiosperm flora colonized New Zealand and New Caledonia during the Cretaceous with genera such as Nothofagus, Forgesia, and Polyosma.

Many other groups have reached New Caledonia after it separated from Australia. This took place as part of a widespread movement of Indo-Malesian elements that expanded into Australasia during the early and middle Tertiary. Some of these newer flora speciated intensively, and are now among the largest genera on the island. Examples include Phyllanthus, with 111 species, Psychotria with about 85 species, and Eugenia with around 37 species, Flindersia in the family Rutaceae, and Polyosma among others.

Most Gymnosperm species are in rainforest. The Gymnosperms are more common on poor acid soils and unbalanced soils with an excess of magnesium and other phytotoxic elements, derived from ultramafic rocks. 39 species are extant, while 27 are considered extinct. The Gymnosperms are more common on exposed ridges or next to rivers or creeks in floodplains. Their concentration is important at individual locations which provide lifesaving refugia, because environmental conditions make interspecific competition less severe. The bamboo genus Greslania is endemic to New Caledonia, and comprises three or four species. Two of them, G. circinata Balansa and G. rivularis Balansa, are discussed. The genus Greslania was described by Balansa in 1872 with three species: G. montana, G. circinata, and G. rivularis all from New Caledonia. They are found only in the southern part of the island where the soil contains heavy metals, such as iron.

Four genera, Araucaria, Libocedrus, Prumnopitys and Retrophyllum that populate the subantarctic Pacific, have endemic species in New Caledonia. The genus Acmopyle (Podocarpaceae), currently present in New Caledonia and Fiji, is a fossil in Patagonia. There are 13 endemic species of Araucaria, including A. rulei and A. columnaris. The island shares some Araucaria species with Australia's Norfolk Island. Many, if not all current populations are relict.

Angiosperms also include many groups of archaic characteristics that appear as vestiges of an old Gondwanan floral background.

Several genera, belonging to primitive families, are endemic or sub-endemic. Amborella is the monospecific endemic genus of the endemic family Amborellaceae. Others are Hedycarya and Kibaropsis (Monimiaceae), Nemuaron (Atherospermataceae) and Balanops (Balanopaceae). The Winteraceae, of the order Magnoliales, considered the oldest group of angiosperms, is represented by the type Zygogynum with 18 species of an order with fifty genera ranging over the Moluccas islands to northern Australia. Among the families with conducting vessels absent or imperfect, New Caledonia has Atherospermataceae, Amborellaceae, Annonaceae and Winteraceae, representatives of families of Chloranthaceae, such as the genus Ascarina with two species, Piperaceae, with twenty species of genera Piper and Peperomia, and Trimeniaceae with Trimenia neocaledonica.

The importance of the families of Gondwanan origin, both in the number of species and their abundance in different plant communities contrasts with the low representation in indigenous communities of more modern groups such as the Compositae, Gramineae, Labiatae and Melastomataceae.

The groups of Gondwanan origin are the most remarkable flora and include Cunoniaceae, Proteaceae and Myrtaceae. The family of Cunoniaceae has six genera in New Caledonia. Pancheria and Codia are endemic, although the last is known as a fossil in Australia, while Cunonia has 23 endemic species in New Caledonia and one species in South Africa. The other three genera have a Papuan-Australian (Acsmithia), Australian (Geissois), and sub-Antarctic (Weinmannia) distribution.

Proteaceae's two main centers of dispersion are in Australia and Southern Africa and is represented in the archipelago by 43 species. They divide into six endemic genera: Beauprea, Beaupreopsis, Garnieria, Kermadecia, Sleumerodendron and Virotia and three non-endemic genera Grevillea, Knightia and Stenocarpus.

Myrtaceae, although basically Gondwanan in origin, currently ranges throughout the tropical world and has reached the Northern Hemisphere. With 229 species, it is the largest family in New Caledonia. It has two widely-distributed genera, Eugenia and Syzygium. The endemic genera are Arillastrum, Cloezia, Myrtastrum, Pleurocalyptus, and Purpureostemon. The genus Melaleuca is represented by six endemic species and one shared with Australia and Papua New Guinea, Melaleuca quinquenervia, known locally as niaouli.