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Afrikaanse Inligting
Leucadendron nervosum Jonaskop Silver Conebush on the Langeberg
Ld
nerv Phill. & Hutch. is the only species in the Sub-section Nervosa
of Leucadendron. This species was considered a rare relict with a
restricted distribution from 1075-1230 m on the north side of Jonaskop in
the Riviersonderend Mountains (Williams 1972). This seemed for all purposes to
be the last word on the matter, but, as often happens in the fynbos, matters are
not nearly so simple.
After the fire in the Boosmansbos Wilderness Area in February 1988 (see PAN 9: 5), the forester-in-charge at the time, Theo van der Merwe, and I walked the path over the Langeberg from Helderfontein to Witbooisrivier (June 1988). I have previously sampled the vegetation of the area in a survey so was able to assess the "damage". Remarkably, in an otherwise stark landscape, north of Grootberg, a small patch of vegetation had remained unscathed. We investigated this patch and it contained a species of Conebush with which neither of us was familiar. Most of the plants in the population (estimated at 200-250) were fatally scorched or burned, but a few of both sexes had survived. I collected a specimen of leaves and a cone from a female plant (McDonald 1561) and returned with this to the Stellenbosch Herbarium (STE).
Identification of the specimen using Williams' (1972) key led us to Ld nerv. This was verified by Dr John Rourke and Dr Jeremy Midgley, although both noted the strangely non-hairy leaves of the Langeberg specimen. Another trip was made to the site in October 1988 in order to photograph the few surviving plants. Seed shed from the burnt plants had germinated and numerous seedlings were found on the sandy soil. A further collection of both sexes was made (McDonald 1586) and lodged at STE.
Ld nerv can now no longer be regarded as endemic to Jonaskop. However, it is difficult to explain the disjunction between the two populations, separated by 130 km, in similar habitats on different mountain ranges. One could speculate that these are relict populations of a species once more extensively distributed in the Plio-Pleistocene, but there is no evidence to support this hypothesis.
The less hairy character of the leaves may suggest delimitation of a separate subspecies (Ld nerv langebergensis?), but more investigation of the different populations would be necessary. What would be interesting would be the discovery of other populations on the Riviersonderend or Langeberg. Here is a challenge to all SW Cape atlassers who traverse the mountains!
Dave McDonald, NBI, Stellenbosch
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