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Cuprophytes are plants that mostly occur on Cu-rich soil. In South Central Africa, these species are threatened by intensive mining exploitation destroying their habitats. Crepidorhopalon tenuis (Scrophulariaceae) is a tiny annual cuprophyte endemic to the Zambesian center of endemism and is particularly abundant in the Lubumbashi area. We investigate here the ecological niche of C. tenuis through the analyses of its abundance and distribution in relation to soil factors, plant community composition, and anthropogenic perturbations. Soil and vegetation data were collected in seven sites (five metalliferous and two nonmetalliferous). The current study shows that C. tenuis has its ecological optimum on copper-rich soil and can be referred to as an elective pseudometallophyte. This species is rare in primary steppic savanna on natural metalliferous soil. Its frequency and abundance peak in pioneer communities on bare soil. In particular, the species showed a surprising ecological plasticity as it was able to benefit from anthropogenic disturbance and to colonize the large areas of bare, contaminated soil left over by mining activities. Our results strongly suggest that C. tenuis was a very rare species in natural metalliferous communities, restricted to patchy areas of open soil in steppic savanna. Recent anthropogenic habitats may have conservation value for some rare metallophytes with colonizing traits and low competitive ability.

Background and aims-The occurrence of natural plant communities on Cu-enriched substrates over signifi cant areas of the earth's surface is exceptional. In Katanga (D.R.Congo), natural outcrops of copper-rich rocks are colonised by highly original plant communities. A number of plant species have been proposed as possibly endemic to those sites. Here we revise the taxonomic, phytogeographic and conservational status of these plants. Methods-Almost all the herbarium materials of supposed Cu-endemics available in BR and BRLU have been revised and all relevant taxonomic revisions have been consulted. Literature and herbarium data have been supplemented by original observations in the fi eld. Conservational status was established using IUCN criteria based on current and projected variation of population size and number. Key results-Thirty-two taxa are identifi ed as strict endemics of Cu-rich soil in Katanga, i.e. absolute metallophytes. Twenty-four of these are known from one to fi ve localities only. Twenty-three other taxa are identifi ed as broad endemics, i.e. with > 75% of occurrence on Cu-rich soil. Fifty-seven other names formerly used for supposed endemics are rejected either for nomenclatural or phytogeographic reasons. A number of species formerly regarded as endemics have been discovered off copper-enriched substrates due to progress in the botanical exploration of Katanga. The taxonomic value of a number of proposed endemics is still uncertain and requires further research. For a number of taxa, local geographic distribution still remains insuffi ciently known. The low proportion of endemics (c. 5%) in the fl ora of Cu-rich soil in Katanga possibly indicates a recent origin of much of this fl ora. Arguments in favour of neoendemism and relictual endemism, respectively, are discussed briefl y. Ten percent of strict endemics are extinct and 65% are critically endangered, due to actual or projected habitat destruction by copper mining. Endemics restricted to primary habitats may be the most diffi cult to conserve. Several species, mostly annuals, are able to thrive on secondary metalliferous habitats created by the mining industry and may thus be at lower risk. Conclusions-This review emphasizes the high conservation value of the fl ora of Cu-rich soil in Katanga and should help prioritise future conservation efforts.

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This study evaluates the feasibility of using the grass species Rendlia altera, Monocymbium ceresiiforme, Cynodon dactylon, and amendments (compost and lime) for the phytostabilisation of soils contaminated by Cu in the province of Katanga (Democratic Republic of Congo). Species were grown on control and Cu-contaminated plots (artificially contaminated with 2,500 mg kg(-1) Cu) unamended (NA), amended with 4.5 kg compost m(-2) or 0.2 kg lime m(-2). R. altera was also grown on contaminated plots amended with 22.5 kg compost m(-2) or 1 kg lime m(-2). Plant survival, growth, and reproduction were monitored for two years. Cu-concentration in leaves of R. altera and M. ceresiiforme were analysed. pH and extractable Cu (0.01 M CaCl2) in soil were analysed in April 2007 and 2008. Results showed that R. altera seems to be the best candidate because of its highest survival on NA, followed by M. ceresiiforme, while liming was necessary to ensure survival of C. dactylon. Lime increased plant reproduction and reduced Cu accumulation in leaves compared to compost. However, higher survival and number of spikes of R. altera obtained in experiment 2 with 22.5 kg compost m(-2) suggest that lime x compost interactions should be investigated in further studies.