Tulbagh Silkypuff

Taxonomy
Scientific Name
Diastella myrtifolia (Thunb.) Salisb. ex Knight
Higher Classification
Dicotyledons
Family
PROTEACEAE
Common Names
Tulbagh Silkypuff (e)
National Status
Status and Criteria
Endangered B1ab(ii,iii)+2ab(ii,iii)
Assessment Date
2020/02/11
Assessor(s)
A.G. Rebelo, D. Raimondo, L. von Staden & H. Mtshali
Justification
Diastella myrtifolia is a highly localized species, with an extent of occurrence (EOO) of 17-44 km², and an area of occupancy (AOO) of 44 km². It remains at two locations, where it continues to decline due to competition from alien invasive plants.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
This species is endemic to the Waterval Mountains south of Tulbagh in the Western Cape.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Hawequas Sandstone Fynbos
Description
It is localized to seeps and stream sides in Hawequas Sandstone Fynbos, 200-600 m. Mature individuals are killed by fires, and only seeds survive. Therefore generation length is linked to fire cycles. Seeds are released after ripening, and dispersed by ants to their underground nests, where they are protected from predation and fire. This makes this species prone to population fragmentation, as ants do not disperse seeds further than a few metres from the parent plant.
Threats
More than 50% of this species' former habitat was lost to the planting of the Suurvlak plantation, established from 1938 onwards. Since 2000, much of this plantation has been cleared or burnt, but the area remains severely degraded and badly infested by invasive alien species (pines, wattles and hakeas). Two of the remaining subpopulations are threatened by competition from spreading, uncontrolled alien invasive plants. Monitoring of the population around the Tulbagh Waterfall in 2016 observed dense hakea infestations in very close proximity to the subpopulation. There has also been some loss and degradation of habitat in the past due to road construction and infrastructure development (power lines), which led to erosion.
Population

This highly localized endemic formerly occurred in one large continuous subpopulation across the summit plateau of the Waterval Mountains, about a 12 km long range. The population was reduced by more than 50% when commercial timber plantations were established within its habitat, resulting in the fragmentation of the population into three isolated subpopulations. Two of these are very small, consisting of only of a few hundred plants. The third subpopulation has several thousand mature individuals. This species is suspected to have suffered a population reduction of 50-70% through historical habitat loss, but it occurred between 1938 and 1945, which is longer than three generations ago. Although plantation forestry is being phased out in favour of conservation, the habitat remains severely degraded and there has been little to no population recovery following the felling of plantations. A continuing decline is inferred from ongoing habitat degradation and competition from alien invasive plants.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Diastella myrtifolia (Thunb.) Salisb. ex KnightCR B1ab(i,ii,iii,iv,v)c(iv)Raimondo et al. (2009)
Diastella myrtifolia (Thunb.) Salisb. ex KnightRare Hilton-Taylor (1996)
Diastella myrtifolia (Thunb.) Salisb. ex KnightRare 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.


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., von Staden, L. & Mtshali, H. 2020. Diastella myrtifolia (Thunb.) Salisb. ex Knight. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2020/08/10

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Distribution map

© C. Paterson-Jones


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