This BioProvince (as defined by Armen Takhtajan) comprising the islands of New Caledonia, the Loyalty Islands and the Isle of Pines has been described as a sub-biokingdom in its own right because of its high levels of endemism right up to family level. The geology includes a band of Palaeozoic rocks running from northwest to southeast for the whole length of the island and a broken band of Mesozoic beds along most of the southwestern coast. The hot, humid, tropical climate is moderated by southeast trade winds. The rich flora includes several endemic families including Amborellaceae, Austrotaxaceae, Oncothecaceae, Phellinaceae and Strasburgeriaceae, about 130 endemic genera, and of the 2700 seed plants, 90% (2500) are considered endemic. Indeed, there is no other area on Earth of comparable size that has such a concentration of endemic families and genera. Only the Hawaiian Islands and Juan-Fernandez Island have higher percentages of endemic genera. In addition many of the endemic genera are not monospecific - some have several tens of species indicating that the flora is extremely ancient. This is also indicated by the presence of a considerable number of archaic taxa including a wealth of gymnosperms and of the 12 known vesseless woody genera of flowering plants possibly 5 (Amborella, Bubbia, Drimys, Exospermum and Zygogynum) occur in this BioProvince. In fact, Amborella trichopoda is thought to be one of the most ancient flowering plants on Earth and a close living relative to the first angiosperms. There are 3 endemic conifer genera (Austrotaxus, Neocallitropsis and Parasitaxus) and the island provides home for nearly half of the World’s species of Araucariaceae (18 out of 44). Parasitaxus ustus is the World’s only known parasitic conifer, and in terms of numbers of endemic conifers, only much bigger areas such as California, New Zealand and Sichan have comparable levels.
The exceptional levels of biodiversity and endemism in this BioProvince are probably related to its variety of soils, habitats and microclimates and to its long period of separation from other landmasses. In fact, it has probably been isolated for some 55 million years. Ultramafic substrates (peridotites and serpentinites) cover about a third of the area and give rise to ultrabasic soils rich in Fe and Mg and several heavy metals such as Ni, Cr, Co and Mn, which are normally toxic to plants. However, much of New Caledonia’s plant life is adapted to these soils and some species are only found on these soils. It has been argued that many of the more primitive groups of plants have survived because of this adaptation since it provides a sort of ecological refugium in which more recently arrived taxa found difficult to adapt to. There is also a specialised flora associated with the calcareous substrates. The flora has much in common with the Indomalesian flora especially those of the New Hebrides, Fiji, New Guinea and the Solomon Islands but there are also Australian and New Zealand elements. However, Eucalyptus is not present suggesting that the separation of New Caledonia from the landmass that gave rise to Australia predates the evolution of this group.
The following accounts for this BioProvince have been written or will be written with particular reference to endemic and locally important species. Accounts available are displayed in green or yellow. Those displayed in red are either in the pipeline or awaiting expert contributions.
|Endemic Vascular Plant Flora|