XVI International Botanical Congess

New Caledonia, an island of continental origin, contains a large number of freshwater aquatic habitats (rivers, lakes, ponds and swamps). The geological history of this territory has led to the formation of very diverse substrate types (ultramafic, calcareous, schist-sandstone, siliceous) to which many New Caledonian species are restricted. Unlike terrestrial species, which are particularly diverse (ca. 3200 native spp.) and highly endemic (ca. 77%), vascular aquatics are poorly represented (ca. 40 spp.), with only a few endemics. Heliophiles (especially Cyperaceae) are mostly cosmopolitan pantropical elements. An account is given of those species strictly limited to ultrabasic substrates. Most species of native vascular aquatic plants are found in neighboring territories with which anew Caledonia=s flora shares its closest affinities, in particular Australia.