Tile-leaf Clusterhead

Taxonomy
Scientific Name
Sorocephalus imbricatus (Thunb.) R.Br.
Higher Classification
Dicotyledons
Family
PROTEACEAE
Common Names
Tile-leaf Clusterhead (e)
National Status
Status and Criteria
Critically Endangered B1ab(iii,v); C2a(ii)
Assessment Date
2020/08/13
Assessor(s)
A.G. Rebelo & D. Raimondo
Justification
Sorocephalus imbricatus has an extent of occurrence (EOO) of 85 km², remaining subpopulations are small and the population is considered to be severely fragmented. There are fewer than 160 mature individuals remaining and decline is ongoing. Most subpopulations have fewer than 10 mature individuals and high mortality of immature and mature individuals has been observed. It is threatened by afforestation, alien plant invasion, too frequent fire and dam construction. It therefore qualifies for listing as Critically Endangered under criteria B and C.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
This species has a limited distribution in mountains of the Western Cape Province in South Africa, where it occurs on the Elandskloof mountains. It was historically also recorded from the Piketberg and Groot Winterhoek mountains but no longer occurs there.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Piketberg Sandstone Fynbos, Winterhoek Sandstone Fynbos, Hawequas Sandstone Fynbos
Description
It grows in sandstone fynbos and montane shale bands, at an altitude of 330-860 m. Mature individuals are killed by fires, and only seeds survive. Seeds are released after ripening, and dispersed by ants to their underground nests, where they are protected from predation and fire. It is pollinated by insects. This species appears to be both a fire ephemeral, rapidly dying after setting seed, and a generation skipper, with many patches not recruiting consistently after fires. It is not known if the latter trait is a feature of the fires (too cool or wrong season, or wrong conditions during potential germination) or the seed banks (as a predator or fungal escape strategy).
Threats
It is threatened by habitat loss to dam construction (pump storage) and forestry plantations. There is ongoing habitat degradation due to too-frequent fires and invasion by alien plants. The subpopulations are very small in size and dormant and are therefore likely to be missed in vegetation surveys and EIAs.
Population

Of the three localities where this species is known to occur, only one population is extant in Tulbagh Waterfall/Suurvlak, where 6 patches of plants occur over a 14 km range. Numbers of mature individuals in 1996 were: 1, 4, 9, and three patches of between 10-50 plants. One of the latter 10-50 plant patches in 1996, had no plants in 2002, despite extensive searching. Three of these patches occur immediately adjacent to the former Suurvlak (Kluitjieskraal) pine plantations and are impacted by ongoing habitat degradation from invasive species. The historically recorded subpopulations from the Piketberg and Groot Winterhoek have not been recorded since the collections by Bolus in the early 1900s.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Sorocephalus imbricatus (Thunb.) R.Br.CR B1ab(i,ii,iii,iv,v)c(iv); C2bRaimondo et al. (2009)
Sorocephalus imbricatus (Thunb.) R.Br.Endangered Hilton-Taylor (1996)
Sorocephalus imbricatus (Thunb.) R.Br.Endangered Hall et al. (1980)
Bibliography

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.


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.


Manning, J.C. and Goldblatt, P. 2012. Plants of the Greater Cape Floristic Region 1: The Core Cape Flora. Strelitzia 29. South African National Biodiversity 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.


Rebelo, T. 2001. Sasol Proteas: A field guide to the proteas of southern Africa. (2nd ed.). Fernwood Press, Vlaeberg, Cape Town.


Citation
Rebelo, A.G. & Raimondo, D. 2020. Sorocephalus imbricatus (Thunb.) R.Br. National Assessment: Red List of South African Plants version . Accessed on 2024/04/14

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Distribution map

© C. Paterson-Jones


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