Cadiscus aquaticus

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Taxonomy [top]

Kingdom Phylum Class Order Family
PLANTAE TRACHEOPHYTA MAGNOLIOPSIDA ASTERALES COMPOSITAE

Scientific Name: Cadiscus aquaticus
Species Authority: E.Mey. ex DC.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B2ab(i,ii,iii,iv,v) ver 3.1
Year Published: 2010
Date Assessed: 2007-07-18
Assessor(s): Helme, N. & Raimondo, D.
Reviewer(s): Sieben, E. & Foden, W.
Justification:
The species is endemic to the Western Cape between Groenekloof and Saldanha Bay and has a highly restricted area of occupancy (<10 km2) as its habitat is vernal pools (50x50 m). It has many severe threats; overgrazing by livestock, infilling of wetlands, invasion by alien grasses and eutrophication. The species is severely fragmented and has declined by >70% in the past 100 years. It is therefore listed as Critically Endangered.

Geographic Range [top]

Range Description:Endemic to Western Cape, South Africa between Eendekuil to Tygerberg (Goldblatt and Manning 2000).

Known localities:
1) 4 km NW of Philadelphia, Schoongezicht farm (Manning 2006)
2) Cape Town. Tierhoogte Farm, about 2 km west of Philadephia.
3) Cape Town. Vernal pools 13 km east of Hopefield (Goldblatt 1997) also seen by CREW in 2005 population highly threatened by alien grasses and infilling of pool by farmer subpopulation expected to be extinct in the next two years.
4) Clanwilliam. Duikerfontein. NW Sandveld (Van Jaarsveld 1987) - likely to be extant
5) Dwars in die Weg, 1 km SE of Eendekuil. 32°45' 27" S and 18°52'32.4" E. Small population of about 100 plants (Helme 2007) / Bellville, Tygerberg, in pools. (Compton 1947) - extinct
6) Piquetberg. The Pools, Piquetberg District. 17 miles NNW of Porterville (Lewis 1937) and (Compton 1937) - extinct searched for unsuccessfully by CREW volunteers and D. Raimondo in 2006
7) Malmesbury District. ½ mile east of Mamre Road station, on Road between Darling and Malmesbury (Rourke 1968) - possibly extant but area highly transformed and consisting now of dense stands of acacias
8) Cape Peninsula. Porterville (Schlechter 1894) - extinct
9) Kalabaskraal - possibly extinct
Countries:
Native:
South Africa (Western Cape)
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: Although there are still many vernal pools remaining on the Swartland most of these do not have C. aquaticus. This species is obviously not able to disperse easily.

Estimated total population size: >1,000;
Estimated number of locations: 4;
Estimated number of past locations: >10;
Estimated number of subpopulations: 4;
Overall populations decline (past): yes > 70% in past 100 years;
Overall population decline (current): yes; Ongoing; yes.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Vernal pools on shale. Juveniles submerged, adults floating, emergent or temporally terrestrial (Cook 2004). Flowering from August to September. Disseminules cypselas with hairs below and bristles above, dispersal unknown but not by wind.
Systems: Freshwater

Threats [top]

Major Threat(s): Livestock grazing and trampling especially by cattle and horses has likely led to the loss of this species in many of its historic localities. Infilling of wetlands and mechanical damage by heavy machinery is considered as a severe ongoing threat. Other less severe threats are invasion by alien grasses caused by dumping of cattle feed in dry pools during summer and eutrophication (run-off from fertilizers used on surrounding ploughed lands).

Conservation Actions [top]

Conservation Actions:

No conservation measures are in place. Site management plans, and law and policy actions to protect the species habitat are urgently needed.

Bibliography [top]

Cook, C.D.K. 2004. Aquatic and wetland plants of southern Africa. Backhuys Publishers, Leiden, The Netherlands.

Goldblatt, P. and Manning, J. 2000. Cape Plants: A conspectus of the Cape Flora of South Africa. Strelitzia, Pretoria.

IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.3). Available at: http://www.iucnredlist.org. (Accessed: 2 September 2010).

South African National Biodiversity Institute. 2007. PRE (National Herbarium, Pretoria) Computerised Information System.


Citation: Helme, N. & Raimondo, D. 2010. Cadiscus aquaticus. In: The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 December 2014.
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