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Oryza neocaledonica 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Cyperales Gramineae

Scientific Name: Oryza neocaledonica Morat

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(iii)+2ab(iii) ver 3.1
Year Published: 2010
Date Assessed: 2007-05-15
Assessor(s): Hequet, V.
Reviewer(s): Pollock, C.M. & Hilton-Taylor, C.
Justification:
Oryza neocaledonica is the most eastern wild rice species in the Pacific; the oriental limit of the genus Oryza, before the recent discovery of this endemic New Caledonian species, was Australia. Its area of occupancy (AOO) is 6 km² and extent of occurrence (EOO) 785 km². The species is known from four separate locations; it occurs along streams or in thalwegs as scattered tufts. Its habitat is among the most threatened in New Caledonia; dry forests have been reduced dramatically, both in size and quality. They have been severely cleared for agricultural purposes over the last century and what remains today are highly fragmented patches that suffer intense predation by the introduced Rusa Deer (Cervus timorensis russa) (de Garine 2005) and uncontrolled fires. The reduction of dry forests has been estimated at 95% over the last 150 years (Bouchet 1995) and this degradation continues today. Based on those data, and because Oryza neocaledonica is always very localized, it is suspected that a population reduction of at least 70% has occurred over this time period. However, since generation length is not known for this species, and it is likely that three generations for this plant is much shorter than 150 years, criterion A has not been used for this assessment.

Geographic Range [top]

Range Description:This species only occurs in the northern half of New Caledonia. It is known from one location in Pouembout in the fenced reserve of Tiea (with some individuals outside), and two in Poum in the banks of Nehoue river and in Ougne forest. The distance between the site of Pouembout and those of Poum is 110 km. Its total extent of occurrence is 785 km², and its estimated area of occupancy within this range is 6 km².
Countries occurrence:
Native:
New Caledonia
Additional data:
Estimated area of occupancy (AOO) - km2:6
Number of Locations:4
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population size is unknown. There are only four known subpopulations, even though surveys have been carried out for this species. When present, individuals form small bushes that can be common or scarce but are usually confined over small surfaces. This pattern can be due to poor long distance dispersal or vegetative reproduction by suckers. The Pouembout subpopulation is small with a few scattered individuals; the Nehoue subpopulation consists of many individuals distributed all along the stream. The last location is known only from the herbarium collection. Because of the distance between sites, there may not be much genetic exchange between subpopulations, especially if Oryza neocaledonica is autogamous, as is the cultivated rice.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species inhabits tropical dry forests which are probably among the world’s most endangered of all lowland tropical forests. Because of their propensity to become pastures and their susceptibility to fire, dry forests have reduced dramatically, in size as well as in quality. In New Caledonia, they’ve been intensively cut for agricultural purposes for a century; what remains today are highly fragmented patches that have been estimated at 2% of the original area. Inside its habitat, Oryza neocaledonica is usually found along river banks or valley. It regenerates well but it is always intensively grazed (J-M Veillon pers. comm.).
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Threats [top]

Major Threat(s): The major threat is lowland clearing for cattle grazing and agriculture, which began in the 1850s and is ongoing. Another threat comes from the Rusa Deer (Cervus timorensis russa), which was introduced in the 1880s and adapted extremely well to the Caledonian habitats. Its population may have reached 105,000–110,000 individuals in the wild. This deer consumes a wide variety of plant species and also causes severe damage to trees by rubbing antlers against tree stems. The third major threat is uncontrolled fires that sweep across lowlands of New Caledonia each year during the dry season and have slowly transformed remnant patches of dry forest into shrubland dominated by Acacia spirorbis and Leucaena leucocephala, or Niaouli (Melaleuca quinquenervia) savannas.

Conservation Actions [top]

Conservation Actions: The presence of this wild rice has motivated the creation of a 32 ha reserve to protect the Tiéa subpopulation (Pouembout).

Citation: Hequet, V. 2010. Oryza neocaledonica. The IUCN Red List of Threatened Species 2010: e.T177819A7464375. . Downloaded on 21 November 2017.
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