Oxalis natans 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Oxalidales Oxalidaceae

Scientific Name: Oxalis natans L.f.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B2ab(i,ii,iii,iv,v) ver 3.1
Year Published: 2010
Date Assessed: 2006-11-17
Needs updating
Assessor(s): Dreyer, L., Oberlander, K., Bayer, B., Zietsman, J. & Raimondo, D.
Reviewer(s): Helme, N. & Foden, W.
This species is only known from two sites; Stellenbosch (Chelchim farm) and Elandsberg Private Nature Reserve in South Africa. It has an area of occupancy of less than 4 km2 and is severely fragmented. Of the two remaining sites, one is experiencing habitat decline and is showing a significant decline in ability to set seed. More than 90% of previous locations are no longer extant. It is therefore listed as Critically Endangered.

Geographic Range [top]

Range Description:Currently distributed from Stellenbosch to Somerset West and Elandsberg, South Africa. Historically distributed from Piketberg to Cape Peninsula and Worcester (Cape Plants 2000).

Two extant localities:
1) Stellenbosch (Chelchim farm), owner keen to conserve (K. Oberlander pers. comm.).
2) Elandsberg Private Nature Reserve. - extant (D. Raimondo pers. obs. 2006) and numerous historic collections.

Extinct localities: note all Salter's historic localities have been searched for by B. Bayer and could not be found, this species has lost the majority of its localities in the past hundred years.
1) Cape Peninsula, Wynberg Dist. Doornhoogde on the Cape Flats - extinct
2) Cape Peninsula, Kenilworth Flats - extinct
3) Cape Peninsula, Wynberg Flats - extinct
4) Piquetberg Road - extinct
5) Wynberg Church between German Church and Golf Links - extinct
6) Cape Flats and Princess Vlei - extinct
7) Claremont Flats - extinct
8) Stellenbosch Dist, Uitspan, northwest of Koelenhof - extinct
9) 12 miles south of Worcester - extinct
10) Cape Peninsula. Kenilthworth Race Course - extinct
11) Stellenbosch Dist. Uitspan, northwest of Koelenhof - extinct
12) Bredasdorp. The Poort - extinct
13) Cape Town. Grassy Park - extinct
Countries occurrence:
South Africa
Additional data:
Estimated area of occupancy (AOO) - km2:<4(500mx500matbothlocations)
Lower elevation limit (metres):50
Upper elevation limit (metres):200
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Estimated total population size: >10 000;
Estimated number of locations: 2;
Overall populations decline (past): yes;
Overall population decline (current): yes; Ongoing; yes
Current Population Trend:Unknown
Additional data:
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:Seasonal pools, at altitudes of 50 - 200 m.

Threats [top]

Major Threat(s): Loss of habitat to urbanisation and agriculture is a severe past threat as >90 % of locations have been lost to these threats. Inbreeding depression, the subpopulation occurring in the disturbed area at Chelchim farm has shown significant decline in ability to set seed with less than 5% of plants naturally setting seed. 10 % of plants are handpollinated. This is completely contrary to the subpopulations at Elandsberg that have high natural seed set.
Threatened in the long term by erosion of the seasonal streams. Cutback erosion leading from furrows in the adjoining ploughed fields are already apparent. This species appears to require very slow flowing water to survive. It is highly sensitive to eutrification and changes in hydrological flow. This is the suspected cause of loss of the Cape Flats populations (B. Bayer pers. com. 2006)

Conservation Actions [top]

Conservation Actions: Part of the species remaining range is within the Elandsberg Nature Reserve.

Citation: Dreyer, L., Oberlander, K., Bayer, B., Zietsman, J. & Raimondo, D. 2010. Oxalis natans. The IUCN Red List of Threatened Species 2010: e.T185407A8405222. . Downloaded on 20 June 2018.
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