Taxonomy
Scientific Name
Geissorhiza darlingensis Goldblatt
Higher Classification
Monocotyledons
Family
IRIDACEAE
National Status
Status and Criteria
Critically Endangered B1ab(iii,v)
Assessment Date
2023/06/20
Assessor(s)
P. Goldblatt, J.E. Victor, I. Ebrahim, R.C. Turner & T. Patel
Justification
This species has an extent of occurrence (EOO) and an area of occupancy (AOO) of 12 km². It is known from three severely fragmented subpopulations and the population is declining. It is therefore listed as Critically Endangered under criterion B.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
It is restricted to the immediate vicinity of Darling, north of Cape Town in the Western Cape province of South Africa.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Swartland Granite Renosterveld
Description
It occurs on damp sandy ground.
Threats
This species has lost 83% of its habitat (calculated using landcover data in GIS). The only known subpopulation of this species is confined to a tiny nature reserve of 20 hectares surrounded by crop fields. A number of threatened lowland renosterveld endemics occur in this reserve, however, the habitat is increasingly impacted by invasive alien grasses spreading as a result of disturbance and nutrient enrichment due to runoff from nearby crop fields.
Population

It is known from three small severely fragmented subpopulations and the population is declining. In 2004 between 100 and 250 plants were recorded at Tinie Versveld Nature Reserve. Subsequent visits in 2005 and 2007 recorded only between 10 and 50 plants. However the monitoring numbers increased again with between 500 and 1000 individuals recorded in 2013. Numbers dropped in 2017 due to dry conditions but have been present at between 150 and 200 individuals again between 2018 and 2022. It is likely that during unfavourable years, plants remain dormant and do not flower, making accurate monitoring very difficult. Twenty years of monitoring data shows that the population fluctuates in response to rainfall, however the overall population is declining at a slow rate due to ever increasing eutrophication and alien invasive grasses. There are two other small subpopulations of fewer than 50 plants known, the one occurs at the farm Baarhuis and the other in a small road side fragment 4 km east of the well known subpopulation at Tinie Versveld Nature Reserve.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Geissorhiza darlingensis GoldblattCR B1ab(iii)+2ab(iii); C2a(ii)Raimondo et al. (2009)
Geissorhiza darlingensis GoldblattIndeterminate Hilton-Taylor (1996)
Bibliography

Duncan, G. 2002. Just holding on: spectacular geophytes in peril. Veld & Flora 88(4):142-147.


Goldblatt, P. 1985. Systematics of the southern African genus Geissorhiza (Iridaceae-Ixioideae). Annals of the Missouri Botanical Garden 72(2):277-447.


Goldblatt, P. and manning, J.C. 1995. New species of the southern African genus Geissorhiza (Iridaceae: Ixioideae). Novon 5(2):156-161.


Goldblatt, P. and Manning, J.C. 2000. Cape Plants: A conspectus of the Cape Flora of South Africa. Strelitzia 9. National Botanical Institute, Cape Town.


Goldblatt, P. and Manning, J.C. 2020. Iridaceae of southern Africa. Strelitzia 42. South African National Biodiversity Institute, Pretoria.


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


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.


Citation
Goldblatt, P., Victor, J.E., Ebrahim, I., Turner, R.C. & Patel, T. 2023. Geissorhiza darlingensis Goldblatt. National Assessment: Red List of South African Plants version . Accessed on 2024/06/14

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Distribution map

© J.C. Manning

© I. Ebrahim

© J.C. Manning


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