Hymenasplenium neocaledonicum is an endemic saxicolous fern from New Caledonia, where it is only known from two recent collection on Grande Terre and Lifou (Loyalty Islands), as well as several ancient collections. It has been observed on damp rocks beside a river in low elevation dense humid forest on volcano-sedimentary substrate. Its extent of occurrence (EOO) and area of occupancy (AOO) are 7,616 and 12 km², respectively. Its habitat does not seem to be threatened at the moment, but some of the ancient localities might have disappeared (Canala, Isle of Pines). It is difficult to get exact localities for these ancient sites, and so identification of specific threats at these sites is not possible. If such threats that caused these disappearances were to emerge at other sites then this species could quickly be driven to Endangered, but there is some uncertainty. Overall, H. neocaledonicum is precautionarily listed as Near Threatened (NT), close to Vulnerable under criteria D2.

Geographical area

H. neocaledonicum is endemic to New Caledonia, where it is known from two recent collections near Hienghène (north-eastern Grande Terre) and Lifou (Loyalty Islands), as well as ancient collections near Canala, on the Isle of Pines and Maré (Loyalty Islands). The sites near Canala and on the Isle of Pines may no longer be extant, but human pressures on Maré have been lower, and so it could persist there.

Population

Population size is unknown, but field observation indicate that this species is fairly common in the Hienghène locality.

Habitat

On Grande Terre, this saxicolous fern has been observed on shaded damp rocks beside a river in low elevation dense humid forest on volcano-sedimentary substrate. In the Loyalty islands, its habitat is still poorly known.

Threats

This species and its habitat do not seem to be significantly threatened, but some of the ancient localities have not been found in over a century and might have disappeared. It is difficult to get exact localities for these ancient sites, and so identification of specific threats at these sites is not possible.

Conservation

H. neocaledonicum is not protected by legislation in New Caledonia and does not occur in any protected areas. In order to clarify its habitat, distribution and threat status, prospection is strongly recommended to find this species in the ancient locations (Canala, Isle of Pines), where it has not been observed in over a century. Besides, taxonomic doubts remain regarding its similarity with H. perriei, found in Fiji.

Bibliography

Xu, K.-W. et al. 2019. A revision of the Hymenasplenium unilaterale subclade (Aspleniaceae; Pteridophyta) with the description of nine new species. Phytotaxa(419 (1)) , p.001-027.

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

Brownlie G. 1969. Flore de la Nouvelle-Calédonie et Dépendances, Volume 03 : Pteridophytae.

Munzinger J., Morat Ph., Jaffré T., Gâteblé G., Pillon Y., Rouhan G., Bruy, D., Veillon J.-M., & M. Chalopin. 2019. FLORICAL: Checklist of the vascular indigenous flora of New Caledonia..

Experts

Assessor(s): Amice, R., Butin, J., Cazé, H., Fleurot, D., Garnier, D., Héquet, V., Perrie, L., Suprin, B., Vandrot, H.

Reviewer(s): Rouhan, G.

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