CFC Code: 46974
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CFC Code: 46974 |
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The African Violet Saintpaulia around Kambai By Diana Percy One of the most prized endemic plant species coveted in the Eastern Arc Mountains is the African Violet, Saintpaulia. The Usambara Mountains harbour 13 of the 20 known species. Many households in Britain and America have at one time played host to this popular house plant. It is therefore strange to realise that the wild source of such a common and well loved 'pet' plant, could have a severely limited and threatened distribution. The Eastern Arc Forests incorporating seven mountainous refugia has a biblical ring; 'edens' of virgin forest; that can be entirely justified by the covenant of rare and endemic species found within these ranges. This continental archipelago of forest islands contain biota greater than 10 million years old. It was around this period that the general aridification of the African continent started to change a richly forested pan-tropical belt, to what is now dry savannah, scrub and woodland. The unique geographical location of the Arc mountains - highlands on an otherwise flat coastal plain, ensure that these ranges are the first recipients of moisture carried inland from the Indian Ocean. The African Violet, Saintpaulia was discovered in 1892 in the Usambara (Tanga) Region by Baron von Saint Paul Illaire. The first specimen was named ionantha, and like all Saintpaulia it is restricted to the moist cool forest habitats of East African coast. Although the majority of cultivated Saintpaulia are derived from a limited gene pool of only two species, it is estimated that 20 different species of Saintpaulia exist in the wild. A full taxonomic investigation has not been undertaken since the early 60's and much new information now needs to be incorporated into a current revision. Out of these 20 taxa, an estimated 13 species are to be found in one range of the Arc mountains - the Usambaras, and 8 of these 13 species are endemic to the East Usambaras. Recent surveys have shown that the habitat of Saintpaulia is largely restricted to gneiss or limestone rocks, and steep slopes near water courses. Kambai forest, an area of 1,010 hectares, maintains a permanent water source in the Miembeni River with several other smaller seasonal water courses. The combination of rapid altitudinal (from 150m - 780m) and microhabitat variation certainly ensures that Kambai harbours a number of other Saintpaulia species in addition to Saintpaulia diplotricha. The many rocky outcrops, provide the reserve with numerous sites typically preferred by Saintpaulia. Already noted, are variations in flower colour from the more common opaque, milky purple to a rarer, deep violet; and variations in leaf from larger sparsely haired to small, compoundly orbicular leaves with long, dense white hairs on the upper surface. There are habitat variations from large rock faces some distance from water courses (some 2 or 3 kilometres in some cases), to rock boulders in the centre and edges of the Miembeni River bed. Saintpaulia have been found growing in the nobbled trunks of the globally threatened cycad plant Encepharlatus hildebrantii and in the crooked branches of Pandanus palms. These habitats provide the essential shade and degree of moisture required. While it is known that different species of Saintpaulia may be found in the same location, hybridisation is common and besides confusingbotanists, this promiscuity is seen as a threat to critically endangered species such as the highly isolated S. tongwensis, limited to only four known sites in a few square kilometres of forest. The difficulties in assessing the taxonomic status using morphological characters alone may now only be clarified with molecular investigations. The growth habit of Saintpaulia is typically precarious, where only a very superficial root system attaches the plant to its surface, and the soft, fleshy vegetation is easily damaged; there maybe some threat from unmonitored human curiosity and 'tourism'. But a much more immediate threat is that of disturbance from reduction in forest canopy cover destroying the essential shaded habitat. This threat is growing, and needs to be tackled at the community level to prevent the further logging and clearing of forest trees. Where trees have been removed, creating 'gaps' around Saintpaulia sites, dissected and dying individuals can be found. Another potential effect of clearing, is the establishment of invasive species such as Maesopsis emnii already present at the forest edge. Maesopsis does not provide the closed canopy required to maintain a moist microclimate on the forest floor. It is not only Saintpaulia that is dependent on such a microclimate but a variety of rare plants and animal species, many of which may still be unrecorded. Diana Percy, is a botanist with the Frontier Tanzania Forest Research Programme, who conducted botanical surveys of three Forest Reserves and a proposed Forest Reserve surrounding Kambai. |
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