Oxalis natans

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
PLANTAE	TRACHEOPHYTA	MAGNOLIOPSIDA	GERANIALES	OXALIDACEAE

Scientific Name:	Oxalis natans
Species Authority:	L.f.

Assessment Information [top]

Red List Category & Criteria:	Critically Endangered B2ab(i,ii,iii,iv,v) ver 3.1
Year Published:	2010
Assessor/s:	Dreyer, L., Oberlander, K., Bayer, B., Zietsman, J. & Raimondo, D.
Reviewer/s:	Helme, N. & Foden, W.
Contributor/s:
Justification: 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:	Native: South Africa
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
Population Trend:	Unknown

Habitat and Ecology [top]

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

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)

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.

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. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 21 May 2013.
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