Retrophyllum minus | Threatened Conifers of the World (en-GB)

Podocarpaceae

Retrophyllum minus (Carrière) C.N.Page

One of two Retrophyllum species endemic to New Caledonia where it is restricted to very few locations in the south of the main island of Grand Terre

Description

Habit

Usually occurs as a small tree up to 3m (rarely up to 9m), trunk characteristically wide at base and tapering upwards to short, stout branches. Bark thick, soft, brown. Branches forming an open, irregular crown, ascending or spreading, usually together at the ned of branches.

Foliage

Leaves spirally arranged, on young shoots arranged in two vertical rows on opposite sides, on mature shoots spreading in different directions, leaf base twisted 90 so that alternating leaves twist in opposite directions (a characteristic of the genus). leaf shape ovate-lanceolate or ovate-elliptic, 10-20 x 2-4mm.

Cones

Male pollen-cones 2-5 and clustered at the end of shoots or solitary in the leaf axil, cylindrical, 4-8 x 2.5-3mm. Female seed-cones terminal with 2-3 pairs of scale leaves with a single, obovoid to pyriform seed, 18-20 x 1.2-1.3 cm. Seed with persistant crest, covered by an fleshy epimatium, gree, or glaucous or white when mature.

Distribution

Endemic to New Caledonia where it is restricted to the Plaine des Lacs area in Province Sud. The population is smaller than 2,500 mature individuals and declining. Its has an extent of occurrence of 255km² with an area of occupancy of about 40km²

Habitat and Ecology

Grows on river banks and lake shores on ultramafic soils at altitudes of 5 to 250m.

Conservation Status

Global assessment

Endangered B1ab(iii,v)+2ab(iii,v);C2a(i)

Global rationale

Retrophyllum minus was once more widespread in southern New Caledonia in the recent past. There has been a significant reduction in the last century due to fires, the construction of dams and mining activities. These threats are ongoing. Currently this species is restricted to a few watercourses and lakes (four locations). Its extent of occurrence is estimated to be 255km² with an area of occupancy of about 40km². The total population is considerably less than 2,500 with no subpopulation estimated to contain more than 250 mature individuals. A continuing decline in mature individuals is projected.

Global threats

The most direct threats come from wild fires and developments associated with mining such as the construction of a major metallurgical plant several kilometres upstream from a major subpopulation. Other longer term threats come from fluctuations in the water flows and the water table.

Conservation Actions

One subpopulation is protected in Chûte de la Madeleine Reserve. Before 1997, this area was freely accessible to the public and was becoming degraded. Since 1997 a management plan has been implemented and some restoration work undertaken. Other subpopulations are not protected.

References and further reading

Cornu, A., Sarrailh, J.-M. & Marion, F. (2001). Espèces endémiques et restauration écologique en Nouvelle-Calédonie. Bois Et Forêts Des Tropique 268(2): 57-68.
de Laubenfels, D. J. (1972). Gymnospermes. In: Aubréville, A. & Leroy, J.-F. (eds.), Flore de la Nouvelle-Calédonie et Dépendances, 4. Paris: Muséum National d’Histoire Naturelle. 167 p.
Jaffre, T., Bouchet, P. & Veillon, J.-M. (1998). Threatened plants of New Caledonia: Is the system of protected areas adequate? Biodiversity & Conservation. 7(1): 36.
Jaffré, T., Munzinger, J. & Lowry, P. P. (2010). Threats to the conifer species found on New Caledonia's ultramafic massifs and proposals for urgently needed measures to improve their protection. Biodiversity & Conservation: 19(5):1485-1502.
Herbert, J., Hollingsworth, P. M., Gardner, M F., Mill, R. R. & Thomas, P. (2002). Conservation genetics and phylogenetics of New Caledonian Retrophyllum (Podocarpaceae) species. New Zealand Journal of Botany 40: 175-188.
Suprin, B. (2011). Florilège des plantes en Nouvelle-Calédonie angiospermes ou plantes à fleurs (lauracées à zingibéracées). Tome 1. Éditions Photosynthèse, Nouméa. 519 pp
Thomas, P. (2010). Retrophyllum minus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. www.iucnredlist.org. Downloaded on 29 June 2012.