The flora of New Caledonia's calcareous substrates

Calcareous substrates occupy c. 3,800 km2 in New Caledonia (incl. 1,990 km2 in the Loyalty Islands) and are of various age and origin. A total of 488 spp. (16.1% of the total indigenous seed plants) grow on these substrates, 39.7% of which are endemic, far below the 76,9% level of the total flora. Among these, 401 spp. are merely tolerant of calcium, with a wide enough ecological amplitude to occupy other substrates, including 200 spp. that also grow on otherwise highly selective ultramafic soils. Only a core of 87 spp. are restricted to calcareous substrates and can truly be called calciphilous. They grow mainly in sclerophyllous and dense forests. The affinities and origins of this flora are analyzed and show stronger links with Australia and Malesia, a result largely similar to those obtained for the floras as a whole. Many threatened taxa are part of this flora, and require special measures to ensure their protection.