Biology
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Cycads are long-lived, slow growing plants that always occur as individual male or female plants (6) (8). There is no way of determining the sex of a cycad until it begins to produce its first cone (8). For a long time cycads were thought, like cone-producing conifers, to be entirely wind pollinated (9). However, studies now suggest that the vast majority, if not all cycads, are actually pollinated by insects or more specifically weevils (6) (8) (9). To attract pollinators, male and female cones produce powerful odours, usually in the early morning or evening (8). Travelling between the sexes, the weevils pollinate the plants by inadvertently transferring pollen from the male cones to the receptive ovules of the female cones (8) (10).
The seeds produced by cycads are large and have a fleshy outer coat, but are relatively short-lived and vulnerable to desiccation. The fleshy outer layer is desirable to a range of animals such as birds, rodents and bats, depending on the species of cycad and region it occupies. However, with any luck the unpalatable seed is discarded some distance away from the parent plant in a hospitable environment in which to germinate (6).
Conservation
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Although the Karoo cycad is listed on Appendix I of the Convention on International in Endangered Species (CITES), which permits trade in this species only under exceptional circumstances, it is not found in any nature reserves (2) (3) (8). If this does not change and the remaining viable populations continue to be illegally exploited by collectors, the Karoo cycad faces the very real threat of extinction in the wild (3).
Description
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The Karoo cycad is one of around 300 living representatives of a plant group, the cycads, which flourished over 150 million years ago alongside the dinosaurs (4) (5). This squat, low-growing species commonly forms clumps with two or more stems branching from the same base (2) (6) (7). Although woody in appearance, the stems are mostly comprised of soft, pithy storage tissue protected by a solid layer of old leaf bases (6) (8). Topping each stem is a crown of long leaves, each comprised of numerous well-spaced, bluish-green or silver leaflets on either side of a central stem (6) (8). The reproductive organs of cycads take the form of cones, similar in appearance to those of a conifer (5), but in the Karoo cycad each stem produces just a singe cone (2). As with all cycads, the male and female cones of this species, both of which are bluish-green (7), are borne on separate plants (8).
Habitat
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Described as the hardiest and most drought resistant of the South African cycad species, the Karoo cycad occurs in semi-arid, low succulent shrubland, subject to very hot summers and cold winters (2) (6) (7). Although rainfall is concentrated during the summer months, it is erratic and the region is prone to prolonged droughts (2) (7).
Range
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The Karoo cycad is endemic to the Eastern Cape Province, South Africa (1) (2) (6).
Status
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Classified as Near Threatened (NT) on the IUCN Red List (1) and listed on Appendix I of CITES (3).
Threats
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While the Karoo cycad was once fairly abundant throughout its range, its numbers have declined dramatically as a result of the growing popularity of this species amongst collectors (7) (8). With the majority of plants in areas close to roads and towns removed, most Karoo cycads are now only found on higher ground in relatively inaccessible terrain (7). Other negative pressures on this species include domestic goats, which damage the leafy crowns, and porcupines, which eat the stem bases in times of drought. Furthermore, there is a weevil species that parasitizes the cones of female Karoo cycads, severely affecting its rate of regeneration (8).
Encephalartos lehmannii
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Encephalartos lehmannii is a low-growing palm-like cycad in the family Zamiaceae. It is commonly known as the Karoo cycad and is endemic to South Africa.[2] The species name lehmannii commemorates Prof J.G.C. Lehmann, a German botanist who studied the cycads and published a book on them in 1834.[2] This cycad is listed as near threatened in the IUCN Red List of Threatened Species.[1]
Description
This cycad grows up to two metres tall with a trunk diameter of up to forty five centimetres and may be branched or unbranched. The leaves are up to one hundred and fifty centimetres long, blue or silver and strongly keeled. The leaflets are lanceolate, do not overlap each other and have smooth margins. The male cones are green or brown and up to thirty five centimetres long. The female cones are a similar colour and up to fifty centimetres long. The seeds are red and up to four and a half centimetres long.[3]
Distribution and habitat
This species is found in Eastern Cape Province, South Africa mainly on dry sandstone slopes and ridges where it grows amongst low succulent herbs and shrubs.[3] By flourishing in such an arid environment it demonstrates how the cycad race has endured through the ages, seemingly immune to drought when many other tree species such as the cabbage trees and taaibos are leafless and sometimes dead.[2]
References
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Encephalartos lehmannii: Brief Summary
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Encephalartos lehmannii is a low-growing palm-like cycad in the family Zamiaceae. It is commonly known as the Karoo cycad and is endemic to South Africa. The species name lehmannii commemorates Prof J.G.C. Lehmann, a German botanist who studied the cycads and published a book on them in 1834. This cycad is listed as near threatened in the IUCN Red List of Threatened Species.
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