Taxonomy
Scientific Name
Disa scullyi Bolus
Higher Classification
Monocotyledons
Family
ORCHIDACEAE
Synonyms
Disa cooperi Rchb.f. var. scullyi (Bolus) Schltr. (in part)
National Status
Status and Criteria
Endangered A2c; C2a(i)
Assessment Date
2012/08/31
Assessor(s)
L. von Staden, D. Raimondo, S.D. Johnson & B. Bytebier
Justification
A formerly widespread and frequently recorded orchid, this species has now become extremely rare as a result of the destruction and disturbance of wetlands. It is estimated that the population has declined by between 60 and 70% in the past 30 years (generation length 10 years). There are currently three known remaining subpopulations, but it is estimated that there could be up to six. Survey data indicates that subpopulations are small, consisting of fewer than 250 mature individuals. The population size is estimated to be fewer than 1500 mature individuals and continues to decline.
Distribution
Endemism
South African endemic
Provincial distribution
Eastern Cape, KwaZulu-Natal
Range
KwaZulu-Natal Midlands around Estcourt southwards along the KwaZulu-Natal and Eastern Cape Drakensberg foothills to the Amathole Mountains near Hogsback.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Mooi River Highland Grassland, East Griqualand Grassland, Drakensberg Foothill Moist Grassland, Lesotho Highland Basalt Grassland, uKhahlamba Basalt Grassland, Southern Drakensberg Highland Grassland, Southern Mistbelt Forest
Description
Wetlands, seepages or stream edges in high altitude grassland, 1 500-2 000 m.
Threats
Habitat loss and degradation as a result of damming, draining and channelling of wetlands to make way for crop fields has resulted in the loss of most subpopulations (Johnson 2006). In other instances, wetlands have been disturbed through overgrazing and trampling by cattle. This species is further threatened by competition from alien invasive plants and development in the KwaZulu-Natal Midlands. Habitat loss and disturbance due to the establishment of forestry plantations is thought to have caused the local extinction of this species in the Hogsback area, where it was last recorded in 1966.
Population

Disa scullyi is a widespread, but rarely encountered habitat specialist. Orchid experts unanimously agree that this species has declined significantly and is in danger of extinction. It was still frequently collected in the 1970s and 1980s, but by the 1990s, it was known from a single subpopulation of about 250 mature individuals in the Eastern Cape, and was believed to be extinct in KwaZulu-Natal (Hilton-Taylor 1996). S.D. Johnson, who studied the pollination biology of this species, spent more than 10 years searching for this species, but could only find this single subpopulation (Johnson 2006), while two other orchid experts (B. Bytebier and H. Kurzweil) spent many years unsuccessfully searching for this species. A population reduction of 60-70% is estimated based on the decline in the number of known subpopulations in the past 30 years (generation length 10 years). Two new subpopulations were recently discovered in KwaZulu-Natal, at one site, which is under negotiation as a biodiversity stewardship site, one plant was seen in 2010, and a subpopulation of between 100 and 200 plants was found in a protected wetland in 2011. At three additional sites where this species was recorded in the past, relatively undisturbed wetlands still remain, and it is possible that some subpopulations still survive. Based on the size of the recently recorded subpopulations, it is estimated that the total population size numbers less than 1500 mature individuals.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Disa scullyi BolusEN A2ac; B2ab(i,ii,iii,iv,v); C2a(i)Raimondo et al. (2009)
Disa scullyi BolusCR A1B1B2Victor (2002)
Disa scullyi BolusEndangered Hilton-Taylor (1996)
Disa scullyi BolusUncertain Hall et al. (1980)
Bibliography

Hall, A.V., De Winter, M., De Winter, B. and Van Oosterhout, S.A.M. 1980. Threatened plants of southern Africa. South African National Scienctific Programmes Report 45. CSIR, Pretoria.


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


Johnson, S.D. 2006. Pollination by long-proboscid flies in the endangered African orchid Disa scullyi. South African Journal of Botany 72(1):24-27.


Linder, H.P. 1981. Taxonomic studies in the Disinae. III. A revision of Disa Berg. excluding sect. Micranthae Lindl. Contributions from the Bolus Herbarium 9:1-370.


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


Pooley, E. 2003. Mountain flowers: a field guide to the flora of the Drakensberg and Lesotho. Natal Flora Publications Trust, Durban.


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.


Victor, J.E. and Dold, A.P. 2003. Threatened plants of the Albany Centre of Floristic Endemism, South Africa. South African Journal of Science 99:437-446.


Citation
von Staden, L., Raimondo, D., Johnson, S.D. & Bytebier, B. 2012. Disa scullyi Bolus. National Assessment: Red List of South African Plants version . Accessed on 2024/07/18

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Distribution map

© R. Braby

© C. Grant

© C. Grant


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