Disa barbata (L.f.) Sw.

Taxonomy
Scientific Name
Disa barbata (L.f.) Sw.
Higher Classification
Monocotyledons
Family
ORCHIDACEAE
Synonyms
Herschelia barbata (L.f.) Bolus, Herschelianthe barbata (L.f.) N.C.Anthony, Orchis barbata L.f., Satyrium barbatum (L.f.) Thunb.
National Status
Status and Criteria
CR C2a(ii)
Assessment Date
2012/08/31
Assessor(s)
L. von Staden, B. Bytebier, W.R. Liltved, E.G.H. Oliver & T.A. Oliver
Justification
This species used to occur on the Cape Flats and the Cape Peninsula, but is now locally extinct in these areas due to habitat loss to urban development. It is now reduced to a single surviving subpopulation in the Malmesbury area. Annual monitoring between 2001 and 2006 indicated that there are ± 110 mature individuals remaining. Continuing decline is occurring due to invasion by alien acacias, and loss of pollinators as a result of incorrect fire management.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
Malmesbury. Extinct on the Cape Flats.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Fynbos
Description
Marshy areas on acid sand flats below 200 m.
Threats
Disa barbata was formerly a very common species on the Cape Flats around Cape Town (Liltved and Johnson, unpubl.) Urban expansion probably caused a population reduction of more than 90%. The last record of this species from the Cape Flats dates from 1950, indicating that the population reduction probably occurred more than three generations ago. Currently one small population survives along the fence line of a small nature reserve near Malmesbury. This nature reserve was formerly densely covered by alien invasive acacias, but these have been largely cleared and re-invasions are being managed. The area outside the reserve fence, where about half the population occurs, is however severely degraded and densely covered in alien invasive plants. Bytebier (2004) has noted that pollination success in the D. barbata population is generally low. The species is pollinated by a specialist carpenter bee, which requires dead wood for nesting sites. Fires provide nesting sites in the fynbos ecosystem, and management in terms of a suitable fire regime is required in the reserve.
Population

The population consists of two clumps, one of about 60 plants inside the reserve, and another of about 50 plants outside the reserve fence. Separated by only a few hundred meters, they are close enough to be considered a single subpopulation. Plants outside the reserve are suspected to be declining due to competition from alien invasive acacias and inappropriate fire management.


Population trend
Decreasing
Notes
Flowering is not fire dependent.
Assessment History
Date
Taxon assessed
Status and Criteria
Citation/Red List version
2009Disa barbata (L.f.) Sw.CR C2a(ii)Raimondo et al. (2009)
2002Disa barbata (L.f.) Sw.VU D2Victor (2002)
1996Herschelianthe barbata (L.f.) N.C.AnthonyE Hilton-Taylor (1996)
Bibliography

Bytebier, B. 2004. Disa barbata. PlantTalk 35:32-33.


Hilton-Taylor, C. 1996. Red data list of southern African plants. Strelitzia 4. South African National Botanical Institute, Pretoria.


Liltved, W.R. and Johnson, S.D. Unpublished. The Cape Orchids - Wild orchids of the Cape Floral Kingdom.


Linder, H.P. 1981. Taxonomic studies in the Disinae. VI. A revision of the genus Herschelia. Bothalia 13(3 & 4):365 - 388.


Linder, H.P. and Kurzweil, H. 1999. Orchids of southern Africa. A.A. Balkema, Rotterdam.


Raimondo, D., von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. and Manyama, P.A. 2009. Red List of South African Plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.


Victor, J.E. 2002. South Africa. In: J.S. Golding (ed), Southern African plant Red Data Lists. Southern African Botanical Diversity Network Report 14 (pp. 93-120), SABONET, Pretoria.


Citation
von Staden, L., Bytebier, B., Liltved, W.R., Oliver, E.G.H. & Oliver, T.A. 2012. Disa barbata (L.f.) Sw. National Assessment: Red List of South African Plants version 2014.1. Accessed on 2014/08/22

Comment on this assessment Comment on this assessment
Distribution map

(c) W.R. Liltved

(c) C. Paterson-Jones

(c) C. Paterson-Jones

(c) B. Bytebier

(c) B. Bytebier

(c) B. Bytebier

(c) I. Ebrahim

(c) I. Ebrahim


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