XVI International Botanical Congess

Calcareous substrates occupy ca. 3500 km2 in New Caledonia (incl. 1990 km2 in the Loyalty Islands) and are of various ages and origins. 500 spp. (16% of the total flowering plant flora of 3100 spp.) grow on these substrates, with endemism at 24%, well below the 77% level of the flora in general. Among these, 410 spp. are merely tolerant of Ca++, with a wide enough ecological amplitude to occupy other substrates, including over 200 spp. that also grow on otherwise highly selective ultramafic rocks. Only a core of 85 spp. are restricted to calcareous substrates, they grow mainly in littoral habitats, as well as scleropyllous and humid forests. The calcareous flora is not particularly rich (3%of the total), but exhibits 41% endemism at the species level. Its affinities and origins are discussed. Numerous threatened taxa occur on calcareous substrates, and merit special protective measures.