The Red Data List status of threatened plants of Gauteng, South Africa is presented. This include... more The Red Data List status of threatened plants of Gauteng, South Africa is presented. This includes evaluations using categories and criteria adopted by the IUCN in 1994 and updated in 2000 for assessing the risk of extinction. A total of 23 taxa were found to be threatened, nine are Data Deficient and 33 former Red Data taxa are not threatened with extinction. The major threat to the continuing persistence of threatened plants in Gauteng is urban development. Recommendations for the conservation of these species are made, and suggestions are given for research needs on certain taxa for which inadequate information is available.
Cycads in South Africa are facing an extinction crisis due to the illegal extraction of plants fr... more Cycads in South Africa are facing an extinction crisis due to the illegal extraction of plants from the wild. Proving wild origin of suspect ex situ cycads to the satisfaction of a court of law is difficult, limiting law enforcement efforts. We investigated the feasibility of using multiple stable isotopes to identify specimens removed from the wild. Relocated and wild specimens from two species in the African genus Encephalartos (E. lebomboensis and E. arenarius) were sampled. (14) C analysis indicated that a ± 30-year chronology could be reliably obtained from the cycads. For E. arenarius, pre-relocation tissue was consistent with a wild origin, whereas tissue grown post-relocation was isotopically distinct from the wild for (87) Sr/(86) Sr and δ(15) N. For E. lebomboensis, δ(34) S, δ(18) O, and (87) Sr/(86) Sr were different between relocated and control plants, consistent with the >30 years since relocation. Our findings demonstrate the potential for a forensic isotope approa...
ABSTRACT While the pollination ecology of many Aloe species is well-documented, knowledge on aloe... more ABSTRACT While the pollination ecology of many Aloe species is well-documented, knowledge on aloe seed ecology, and hence aloe reproductive ecology in its entirety is limited. The aim of this study was to investigate the reproductive ecology of Aloe plicatilis, a Cape fynbos tree aloe endemic to the Cape Winelands, South Africa. Results from a pollinator exclusion experiment conducted at an A. plicatilis population on Paarl mountain suggests pollination primarily by insects, although bird visitation significantly increased seed set/fruit indicating possible co-pollination with insects. The species' long-tubed flowers and production of concentrated nectar, with observations of malachite sunbirds as themost common avian visitors to A. plicatilis flowers indicate the importance of long-billed specialist avian nectarivores as floral visitors. Analysis of the relationship between plant size and inflorescence production for five populations combined revealed a significant, positive linear relationship between plant size and the logarithm of the number of inflorescences/plant. Natural fruit and seed set determined for three populations (1325, 27,930 and 251,616 seeds/population) suggests low reproductive output compared to several other Aloe species. The smallest (31 individuals) and least dense (75 plants/ha) A. plicatilis population produced the lowest seed set/plant (128 seeds) and per population (1325 seeds), suggesting an Allee effect. Evaluation of seed dispersal potential showed that potential dispersal distances were approximately three times the canopy height; however, the occurrence of A. plicatilis on mountains isolated from more continuous mountain ranges on which the species also occurs suggests the possibility of long-distance dispersal by strong, gusty, summer winds. Soil seed bank samples collected from 13 populations yielded close to zero seedling emergence, indicating the absence of persistent seed banks. A. plicatilis seeds stored under ambient laboratory conditions for 3, 18 and 24 months were germinated in an environmental control chamber and a laboratory. High percentage germination was recorded for 18- and 24-month-seed (86 and 80%, respectively), while germination of 3-month-old seeds was three times lower, suggesting the need for after-ripening. Germination of fresh and one-year-old seed under ambient nursery conditions at the Karoo Desert National Botanical Garden in Worcester yielded emergence percentages of 67 and 44%, respectively, and were therefore less successful than germination under more controlled conditions. This is the first known study to investigate the reproductive ecology of a tree aloe species and that of a Cape fynbos aloe. The study highlights the importance of further studies on aloe seed ecology, particularly for rare and threatened species.
... Strelitzia 1 (Ed. BJ HUNTLEY. National Botanical Institute, Pretoria. Hilton-Taylor, C. (1996... more ... Strelitzia 1 (Ed. BJ HUNTLEY. National Botanical Institute, Pretoria. Hilton-Taylor, C. (1996) Red Data List of Southern African Plants. Strelitzia 4. National Botanical Institute, Pretoria. IUCN. (1994) IUCN Red List Categories. IUCN Gland, Switzerland. Lamont, BB. ...
The Red Data List status of threatened plants of Gauteng, South Africa is presented. This include... more The Red Data List status of threatened plants of Gauteng, South Africa is presented. This includes evaluations using categories and criteria adopted by the IUCN in 1994 and updated in 2000 for assessing the risk of extinction. A total of 23 taxa were found to be threatened, nine are Data Deficient and 33 former Red Data taxa are not threatened with extinction. The major threat to the continuing persistence of threatened plants in Gauteng is urban development. Recommendations for the conservation of these species are made, and suggestions are given for research needs on certain taxa for which inadequate information is available.
Cycads in South Africa are facing an extinction crisis due to the illegal extraction of plants fr... more Cycads in South Africa are facing an extinction crisis due to the illegal extraction of plants from the wild. Proving wild origin of suspect ex situ cycads to the satisfaction of a court of law is difficult, limiting law enforcement efforts. We investigated the feasibility of using multiple stable isotopes to identify specimens removed from the wild. Relocated and wild specimens from two species in the African genus Encephalartos (E. lebomboensis and E. arenarius) were sampled. (14) C analysis indicated that a ± 30-year chronology could be reliably obtained from the cycads. For E. arenarius, pre-relocation tissue was consistent with a wild origin, whereas tissue grown post-relocation was isotopically distinct from the wild for (87) Sr/(86) Sr and δ(15) N. For E. lebomboensis, δ(34) S, δ(18) O, and (87) Sr/(86) Sr were different between relocated and control plants, consistent with the >30 years since relocation. Our findings demonstrate the potential for a forensic isotope approa...
ABSTRACT While the pollination ecology of many Aloe species is well-documented, knowledge on aloe... more ABSTRACT While the pollination ecology of many Aloe species is well-documented, knowledge on aloe seed ecology, and hence aloe reproductive ecology in its entirety is limited. The aim of this study was to investigate the reproductive ecology of Aloe plicatilis, a Cape fynbos tree aloe endemic to the Cape Winelands, South Africa. Results from a pollinator exclusion experiment conducted at an A. plicatilis population on Paarl mountain suggests pollination primarily by insects, although bird visitation significantly increased seed set/fruit indicating possible co-pollination with insects. The species' long-tubed flowers and production of concentrated nectar, with observations of malachite sunbirds as themost common avian visitors to A. plicatilis flowers indicate the importance of long-billed specialist avian nectarivores as floral visitors. Analysis of the relationship between plant size and inflorescence production for five populations combined revealed a significant, positive linear relationship between plant size and the logarithm of the number of inflorescences/plant. Natural fruit and seed set determined for three populations (1325, 27,930 and 251,616 seeds/population) suggests low reproductive output compared to several other Aloe species. The smallest (31 individuals) and least dense (75 plants/ha) A. plicatilis population produced the lowest seed set/plant (128 seeds) and per population (1325 seeds), suggesting an Allee effect. Evaluation of seed dispersal potential showed that potential dispersal distances were approximately three times the canopy height; however, the occurrence of A. plicatilis on mountains isolated from more continuous mountain ranges on which the species also occurs suggests the possibility of long-distance dispersal by strong, gusty, summer winds. Soil seed bank samples collected from 13 populations yielded close to zero seedling emergence, indicating the absence of persistent seed banks. A. plicatilis seeds stored under ambient laboratory conditions for 3, 18 and 24 months were germinated in an environmental control chamber and a laboratory. High percentage germination was recorded for 18- and 24-month-seed (86 and 80%, respectively), while germination of 3-month-old seeds was three times lower, suggesting the need for after-ripening. Germination of fresh and one-year-old seed under ambient nursery conditions at the Karoo Desert National Botanical Garden in Worcester yielded emergence percentages of 67 and 44%, respectively, and were therefore less successful than germination under more controlled conditions. This is the first known study to investigate the reproductive ecology of a tree aloe species and that of a Cape fynbos aloe. The study highlights the importance of further studies on aloe seed ecology, particularly for rare and threatened species.
... Strelitzia 1 (Ed. BJ HUNTLEY. National Botanical Institute, Pretoria. Hilton-Taylor, C. (1996... more ... Strelitzia 1 (Ed. BJ HUNTLEY. National Botanical Institute, Pretoria. Hilton-Taylor, C. (1996) Red Data List of Southern African Plants. Strelitzia 4. National Botanical Institute, Pretoria. IUCN. (1994) IUCN Red List Categories. IUCN Gland, Switzerland. Lamont, BB. ...
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