Taxonomy
Scientific Name
Crassula tuberella Toelken
Higher Classification
Dicotyledons
Family
CRASSULACEAE
National Status
Status and Criteria
Vulnerable B1ab(iii)
Assessment Date
2020/02/06
Assessor(s)
L. von Staden & H. Mtshali
Justification
Crassula tuberella is suspected to have a very narrow distribution range, but due to taxonomic uncertainty, its range cannot be accurately defined. Its extent of occurrence (EOO) is possibly as small as 6244 km², but could be up to 22 664 km² if records from the eastern Free State and Lesotho are included. It is known from fewer than 10 locations and is declining across its range due to ongoing habitat loss and degradation.
Distribution
Endemism
Not endemic to South Africa
Provincial distribution
KwaZulu-Natal, Mpumalanga
Range
This species is endemic to a small area on the border between Mpumalanga and KwaZulu-Natal, where it occurs from Ermelo to Glencoe, possibly extending as far as the Leribe district in Lesotho.
Habitat and Ecology
Major system
Freshwater
Major habitats
Low Escarpment Moist Grassland, Northern KwaZulu-Natal Moist Grassland, Wakkerstroom Montane Grassland, Amersfoort Highveld Clay Grassland, Eastern Highveld Grassland
Description
It occurs in shallow vleis and marshes in high altitude montane grassland.
Threats
Grasslands within this species' known range are in poor condition due to loss and fragmentation to crop cultivation, as well as severe overgrazing by livestock. This has caused disruptions of flow dynamics of wetland ecosystems, erosion, as well as eutrophication of vleis and marshes. In addition, around Wakkerstroom, it is potentially threatened by habitat loss and degradation due to proposed coal mining. There are ongoing legal battles to prevent mining in this area, which is likely to severely degrade one of South Africa's most important strategic water sources.
Population

Crassula tuberella is a rare and poorly known species. It is known from three to six locations, but it may be overlooked due to confusion with C. inanis. A continuing decline is inferred from ongoing habitat loss and degradation.


Population trend
Decreasing
Notes
Crassula tuberella is difficult to distinguish from the widespread and common C. inanis (Tölken 1985). The two species overlap in distribution range, but according to Tölken (1985), they occupy different habitats. In his description of the species, Tölken (1975) cites a record from Lesotho, but according to Tölken (1985), C. tuberella has a small distribution range in southern Mpumalanga and northern KwaZulu-Natal. The full extent of this species' distribution range is therefore uncertain, and more field surveys and taxonomic study are needed to resolve it.
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Crassula tuberella ToelkenLeast Concern Raimondo et al. (2009)
Crassula tuberella ToelkenLower Risk - Least Concern Scott-Shaw (1999)
Crassula tuberella ToelkenRare Hilton-Taylor (1996)
Crassula tuberella ToelkenRare Hall et al. (1980)
Bibliography

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


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.


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.


Scott-Shaw, C.R. 1999. Rare and threatened plants of KwaZulu-Natal and neighbouring regions. KwaZulu-Natal Nature Conservation Service, Pietermaritzburg.


Sieben, E.J.J. 2009. The status and distribution of vascular plants (Magnoliophyta, Lycophyta, Pteridophyta). In: W.R.T. Darwall, K.G. Smith, D. Tweddle and P. Skelton (eds.), The status and distribution of freshwater biodiversity in southern Africa (pp. 83-98), IUCN and SAIAB, Gland, Switzerland and Grahamstown, South Africa.


Tölken, H.R. 1975. New taxa and new combination in the genus Crassula. Journal of South African Botany 41(2):93-124.


Tölken, H.R. 1977. A revision of the genus Crassula in Southern Africa. Contributions from the Bolus Herbarium 8(1&2):1-595.


Tölken, H.R. 1985. Crassulaceae. In: O.A. Leistner (ed). Flora of southern Africa 14,1:1-244. Botanical Research Institute, Pretoria.


Citation
von Staden, L. & Mtshali, H. 2020. Crassula tuberella Toelken. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2020/10/20

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