''Gymnostoma'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of about eighteen species of trees and shrubs, constituting one of the four

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

of the plant family

Casuarinaceae The Casuarinaceae are a family of dicotyledonous flowering plants placed in the order Fagales, consisting of four genera and 91 species of trees and shrubs native to eastern Africa, Australia, Southeast Asia, Malesia, Papuasia, and the Pacific ...

. The species grow naturally in the tropics, including at high elevations having temperate climates, in forests in the region of the western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

and

Malesia Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms. It is a phytogeographical floristic region in the Paleotropical kingdom. It was first recognized as a distinct region ...

. In

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

, published botanical science describes eight species found growing naturally, which botanists have not found anywhere else (endemics). Other species are native to

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

, Maluku, and

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

, and one endemic species each in

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

and the

Wet Tropics of Queensland The Wet Tropics of Queensland World Heritage Site consists of approximately 8,940 km2 of Australian wet tropical forests growing along the north-east Queensland portion of the Great Dividing Range. The Wet Tropics of Queensland meets all f ...

, Australia. The genus was first scientifically described by Lawrie A. S. Johnson in 1980. Many of the ''Gymnostoma'' species combinations of names ( binomials) were described by him in 1982. , a global total of eighteen species have been found and described. The majority of the species grow in rainforests, in the habitats of open, sunny, long-term gaps, from river bank (riparian) situations through to mountain top situations. In New Caledonia two endemic species ''G. chamaecyparis'' and ''G. deplancheanum'' have specialised adaptations, growing in wet "shrub maquis and paraforest maquis formations. ''G. chamaecyparis'' is associated with hypermagnesian soils (hypermagnesian

inceptisol Inceptisols are a soil order in USDA soil taxonomy. They form quickly through alteration of parent material. They are more developed than Entisols. They have no accumulation of clays, iron oxide, aluminium oxide or organic matter. They have a ...

) below 600 m altitude at the base of

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usua ...

massif A massif () is a principal mountain mass, such as a compact portion of a mountain range, containing one or more summits (e.g. France's Massif Central). In mountaineering literature, ''massif'' is frequently used to denote the main mass of an ...

s. ''G. deplancheanum'' occurs on ferralitic ferritic desaturated

hardpan In soil science, agriculture and gardening, hardpan or soil pan is a dense layer of soil, usually found below the uppermost topsoil layer. There are different types of hardpan, all sharing the general characteristic of being a distinct soil layer ...

or gravelly soils ( oxisol) on the southern massif at altitudes between 200 and 1,000 m".

Species

There are 14 formally described species: * '' Gymnostoma australianum'' – Australia endemic * '' Gymnostoma chamaecyparis'' – New Caledonia endemic ( Fr) * '' Gymnostoma deplancheanum'' – New Caledonia endemic ( Fr) * '' Gymnostoma glaucescens'' – New Caledonia endemic * '' Gymnostoma intermedium'' – New Caledonia endemic * '' Gymnostoma leucodon'' – New Caledonia endemic * '' Gymnostoma nobile'' – Borneo * '' Gymnostoma nodiflorum'' – New Caledonia endemic * '' Gymnostoma papuanum'' – New Guinea * '' Gymnostoma poissonianum'' – New Caledonia endemic * '' Gymnostoma rumphianum'' – Maluku * '' Gymnostoma sumatranum'' – Sumatra * '' Gymnostoma vitiense'' – Fiji endemic * '' Gymnostoma webbianum'' – New Caledonia endemic There are approximately four additional species, found in New Guinea and collections preserved, that are awaiting formal description.

References

Fagales genera {{Fagales-stub