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Rare plants rediscovered in the Northern Cape

Erich van Wyk (SANBI, Pretoria), Paul Smith (Royal Botanic Gardens, Kew), and Priscilla Burgoyne (SANBI, Pretoria) undertook a trip to the Northern Cape as part of the SANBI/Millennium Seed Bank (MSB) collaboration. The primary objective of the expedition was to collect seeds for the MSB, mainly from the family Mesembryanthemaceae. The secondary goal was to collect any good seeding species endemic to the region.

Mesembs were targeted, as the area is well known for the numerous endemic mesembs, which were in full seed at that time of the year. As an expert on these taxa, Priscilla was co-opted for this purpose. The field trip was a great success in terms of numbers of species and seed collected, despite the unusually hot weather (45ºC in the shade on the shadeless Knersvlakte!). Seed of 72 species was collected, including 46 mesembs.

Of greater botanical interest was the rediscovery of two long-lost plant populations. The first was Dioscorea elephantipes (L’Hérit.) Engl. (Dioscoreaceae), a spectacular shrubby climber up to 1.5 m high with a huge caudex reaching a diameter of up to 0.75 m, mainly exposed above ground. Its reticulated skin resembles that of an elephant, hence the specific name.

Because of its unusual appearance, this attractive plant has been overcollected and is now threatened in the wild. It has not been seen near Komaggas since 1954. Using rough directions provided by Johan Hurter (SANBI, Lowveld National Botanical Garden), our team spent a whole day searching for this elusive species, with no success.

Finally, on the point of giving up, we asked a local shepherd, who immediately recognised the plant we were looking for, and directed us to a very healthy population. On a steep mountainside, we found approximately 1,000 plants concentrated on a scree slope. Although there was no seed, we were able to thoroughly document the location, size, and ecology of the population.

Our second interesting find was Cylindrophyllum hallii L.Bolus (Mesembryanthemaceae) on a plateau near Loeriesfontein. This plant is of great interest as its sister species all come from the Little Karoo. In notes accompanying the original description, the collector H. Hall stated that only about 200 plants were seen. We followed telephoned instructions from Johan du Toit, an amateur succulent enthusiast from George, who directed us to the site of this single known population.

The population has not been documented or collected since 1960, and we were very excited to find it. Only about 219 (see box) living plants were left, with clear signs of predation. We saw many dead plants, possibly victims of drought or utilisation by animals. Fortunately, seed was in ample supply and we were able to collect capsules from some 85 plants very safely, taking less than 5% of what was available.

This is exactly the kind of species that needs ex situ conservation—down to only one known wild population, severely threatened at the site, and a candidate for Red Data listing. The germination protocol for this species will now be worked out to ensure that if the remaining population should die out, seed and the methodology would be available for its reintroduction.

Other exciting finds include flowering specimens of Haemanthus unifoliatus found together with the Dioscorea near Komaggas. Ruschia sandbergensis was found at the Messelpad Pass, southwest of Springbok. Seed collections were made of two Namaqualand endemics, namely Psilocaulon foliosum and Enarganthe octonaria. The latter is a monotypic genus found only in the Richtersveld and northern Namaqualand.

Paul Smith would like to thank the British Airways Assisting Conservation Programme, which enabled him to participate in this expedition.

—by Paul Smith, Priscilla Burgoyne & Erich van Wyk

SABONET News 6.1: 51

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Southern African Botanical Diversity Network.