Metal concentrations have been determined in shoots of 12 species considered as Cu and/or Co hyperaccumulators, collected from five subpopulations in a Cu/Co mine in Katanga. Samples have been subjected to three cleansing protocols (water, alconox, alconox + EDTA). Cu/Co concentrations were significantly higher when demineralised water was used to wash samples compared to more aggressive solutions. Washing effect was largest for species with velvety (Acalypha cupricola) or sticky (Haumaniastrum katangense) indumentum. Element concentrations in shoots varied by two orders of magnitude, i.e. 45-2,891 mg kg −1 Cu (median: 329 mg kg −1 ) and 21-1,971 mg kg −1 Co (median: 426 mg kg −1 ) and were generally lower than previously published values. Only 9.3% of data exceeded the hyperaccumulation threshold (1,000 mg kg −1 ) for Cu and 13% for Co. Shoot concentrations varied by up to two orders of magnitude among subpopulations within species which was partly explained by variation of metal concentrations in the soil. Although the species considered in this paper undisputedly accumulate Co and Cu up to very high concentrations that require specific shoot tolerance mechanisms, the concept of hyperaccumulation, as defined for other metals like Zn and Ni, needs to be critically re-examined for Cu and Co. Our results suggest that many species so far regarded as Co/Cu hyperaccumulators might eventually turn out to be indicators.

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Background and aims Among the unique flora on copper and cobalt rich soils, some species are able to hyperaccumulate the Cu and Co in their shoots, however, the unexplained high variations of Cu and Co concentrations in shoots have been highlighted. A good comprehension of the Cu and Co accumulation variations would go through a characterization of the Cu and Co speciation in soils. We examined the covariations of Cu and Co speciation in soils and Cu and Co concentrations in plants.Methods Plant samples of two species and soil samples (n=146) were collected in seven pedogeochemically contrasted sites. Cu and Co speciation in soils was modeled by WHAM 6.0. Results Variation in copper accumulation in plant shoots were mostly influenced by Cu adsorbed by the Mn and Fe oxides fractions, whereas Co accumulation variations were strongly influenced by Co free and Co adsorbed by the OM and Fe fractions. Conclusions Availability of Cu and Co seems to be species-specific and is not explained only by the free Cu and Co content in the soil solution, but also strongly by the part linked to colloidal fractions. Availability of Cu and Co is a complex mechanism, closely related to all the biogeochemical processes which occur in the rhizosphere. Future work should perform experiments in controlled conditions to examine the soil parameters that influence the Cu and Co availability.

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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