Heterostemma bicanthaceum is an endemic liana from New Caledonia restricted in calcicole, mesic to humid forests of Ile des Pins, Kuébini and Koumac. It grows up to 30 m asl. The subpopulation of Koumac is very impacted by Rusa deer (Rusa timorensis) and is probably extent. Recent prospections at Koumac did not manage to relocate this species. In fact, mesic habitats of the west of Grande Terre are highly affected by Rusa deer overgrazing which contibute to soil erosion (Munzinger & Gâteblé, 2017). This species is not rare at Ile des Pins but it is only occurs in the preserved and rich part of the forest where there is a potential (low) impact of feral pigs (Sus scrofa) and logging operation at Gadji.The subpopulation at Kuebini is not well known but due to its low altitudinal range and the high fire occurence at the region, there is a potentially impact of bushfires. Its Area of Occupancy (AOO) and Extent of Occurrence (EOO) are respectively estimated to be 20 and 115 km² with a number of location equal to 3. Therefore Heterostemma bicanthaceum is considered Endangered (EN) B1ab(i,ii,iii,iv,v) + 2ab(i,ii,iii,iv,v) with a decline of all the concerned subcriteria.

Geographical area

Heterostemma bicanthaceum is an endemic liana from New Caledonia restricted in calcicole, mesic to humid forests of Ile des Pins, Kuébini and Koumac.

Population

Population size is unknown.

Habitat

Heterostemma bicanthaceum occurs in calcicole, mesic to humid forests at calcareous substrates at an altitudinal range of 2 and 30 m asl.

Threats

The subpopulation of Koumac is very impacted by Rusa deer (Rusa timorensis) and is probably extent. Recent prospections at Koumac did not manage to relocate this species. In fact, mesic habitats of the west of Grande Terre are highly affected by Rusa deer overgrazing which contibute to soil erosion (Munzinger & Gâteblé, 2017). This species is not rare at Ile des Pins but it is only occurs in the preserved and rich part of the forest where there is a potential (low) impact of feral pigs (Sus scrofa) and logging operation at Gadji.The subpopulation at Kuebini is not well known but due to its low altitudinal range and the high fire occurence at the region, there is a potentially impact of bushfires.

Conservation

Heterostemma bicanthaceum is not protected by legislation in New Caledonia and it does not occur in a protected area. The New Caledonian Wilderness Conservation Agency (Conservatoire d'espaces naturels), which coordinates the local Invasive Species Programme, should also be informed on the species situation in areas impacted by Rusa deer.

Bibliography

Endemia.nc 2016. Faune et Flore de Nouvelle-Calédonie.

Munzinger J., Morat Ph., Jaffré T., Gâteblé G., Pillon Y., Rouhan G., Bruy, D., Veillon J.-M., & M. Chalopin 2020. FLORICAL: Checklist of the vascular indigenous flora of New Caledonia [continuously updated].

Meve U., Gâteblé G. & Liede-Schumann S. 2018. Two new species from the Ile des Pins (New Caledonia), and a not so new species from Grande Terre (New Caledonia). Phytotaxa(349 (3)) , p.201-213.

LIEDE-SCHUMANN S., MEVE U., GÂTEBLÉ G., BARRIERA G. & FICI S. 2020. Apocynaceae p.p., Phellinaceae, Capparaceae : Flore de la Nouvelle-Calédonie.

Boiteau Pierre avec collaboration de Lucie Allorge 1982. Flore de la Nouvelle Calédonie et dépendances. Volume 10 : Apocynacées.

Experts

Assessor(s): Amice, R., Bruy, D., Butin, J., Cazé, H., Fleurot, D., Héquet, V., Lannuzel, G., Laudereau, C., Mandaoué, L., Vandrot, H., Pillon, Y.

Reviewer(s): Veillon, J.

Facilitator(s): Gâteblé, G., Meyer, S., Warimavute, G.