Taxonomy
Scientific Name
Disa lugens Bolus var. nigrescens (H.P.Linder) H.P.Linder
Higher Classification
Monocotyledons
Family
ORCHIDACEAE
Synonyms
Herschelia lugens (Bolus) Kraenzl. var. nigrescens H.P.Linder, Herschelianthe lugens (Bolus) Rauschert var. nigrescens (H.P.Linder) N.C.Anthony
National Status
Status and Criteria
Critically Endangered B1ab(iii,v)+2ab(iii,v)
Assessment Date
2023/01/25
Assessor(s)
L. von Staden & W.R. Liltved
Justification
This taxon is a highly restricted endemic known from one location near Humansdorp. It has an extent of occurrence (EOO) and an area of occupancy (AOO) of less than 5 km². Habitat quality is declining due to alien invasive plants. This species therefore qualifies for listing as Critically Endangered under criterion B.
Distribution
Endemism
South African endemic
Provincial distribution
Eastern Cape
Range
This taxon is endemic to the Eastern Cape Province, where it is restricted to Oyster Bay near Humansdorp.
Habitat and Ecology
Major system
Terrestrial
Major habitats
St Francis Dune Thicket
Description
Plants grow on coastal sand flats and mountain slopes in grassy fynbos.
Threats
Dairy farming and invasive Acacia cyclops have led to the degradation of the habitat of this taxon (Liltved and Johnson, 2012). The site is also densely infested with invasive alien wattles. This striking 'black' orchid is very popular with collectors; declines during the 1990s were noted due to the removal of individuals from the wild.
Population

This taxon is restricted to a single location, and not much is known about its population size and structure. It was last seen in 1993, and despite targeted searches, it has not been observed between 2003 and 2022. Little is known about its ecology, but fire is likely to be an essential part of its life history. Searches following the fire have not taken place, and ongoing monitoring, especially after the fire, is required to determine the current population size and status. The population is inferred to be declining due to the impact of invasive alien species.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Disa lugens Bolus var. nigrescens (H.P.Linder) H.P.LinderCR B1ab(iii,v)+2ab(iii,v)Raimondo et al. (2009)
Disa lugens Bolus var. nigrescens (H.P.Linder) H.P.LinderVU D2Victor (2002)
Herschelianthe lugens (Bolus) Rauschert var. nigrescens (H.P.Linder) N.C.AnthonyEndangered Hilton-Taylor (1996)
Bibliography

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


Johnson, S. and Bytebier, B. 2015. Orchids of South Africa: A field guide. Struik Nature, Cape Town.


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.


McMaster, C. 2007. Disa lugens: Eastern Cape orchird. Veld and Flora 93, 147-149.


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. & Liltved, W.R. 2023. Disa lugens Bolus var. nigrescens (H.P.Linder) H.P.Linder. National Assessment: Red List of South African Plants version . Accessed on 2024/07/17

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Distribution map

© W.R. Liltved


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