Associate Professor in plant ecology at Polytechnic Institute of LaSalle Beauvais (ISAB-IGAL), in the research team Hydrogeochimical Interactions Soil Environment (HydrISE).
Research interests in ecology and biogeochemistry
- Plant conservation and restoration - Adaptation of plant populations and communities to metalliferous soils - Bioavailability of trace metals and plant ecology
Abstract: Crepidorhopalon perennis is an endemic metallophyte restricted to only one site on Cu-rich soils in Katanga. Crepidorhopalon tenuis has a broader niche, from normal to Cu-rich soils, but has high affinity for cupriferous habitats. Both plants have been considered as Cu-Co accumulators. Cu tolerance and accumulation of C. tenuis were studied in axenic conditions in vitro in four metallicolous populations and one non-metallicolous population whereas for C. perennis only one population was investigated. Results showed a high Cu tolerance of both C. tenuis and C. perennis. Variation of tolerance among metallicolous and non-metallicolous populations was also observed. The addition of Cu enhanced the growth of some metallicolous populations under sterile conditions, hence confirming the high needs in copper of metallicolous populations. This could represent a cost of tolerance which would explain the high affinity of species for cupriferous habitats. On the other hand, Crepidorhopalon perennis did not show the same features. Its restricted distribution may be explained by a cost of Cu tolerance. Crepidorhopalon perennis and C. tenuis are not Cu hyperaccumulators and seem to behave rather like excluders species.
Abstract: Crepidorhopalon perennis is an endemic metallophyte critically endangered by mining activities and currently known from only one site on copper-rich soils in Katanga (D.R. Congo). It is closely related to the annual C. tenuis, also a rare metallophyte, but with a broader geographical range. We investigated the variation in morphometric traits and ecological niches (based on edaphic conditions and pollinator assemblages) of C. perennis and C. tenuis, to evaluate the risk of inter-specific competition, and their potential for hybridization to ascertain if C. perennis may be at risk of genetic swamping by its more widespread congener. We examined whether species were found under sympatric or parapatric settings with opportunity for hybridization (or gene exchange). Such knowledge is essential for implementing restoration management protocols, including the introduction of C. perennis into substitution sites where C. tenuis may be already present. Fourteen morphological characters and 11 soil variables were measured and visiting pollinator species were identified at the site where the two species co-occur. Our results show that the two species can be distinguished based on their morphological traits, show niche overlap based on edaphic properties, and share the same pollinator assemblage. In addition, no morphologically intermediate individuals could be detected, suggesting no hybridization, and that the two species may be reproductively isolated. We conclude that C. perennis conservation and restoration operations can be realized in substitution sites where C. tenuis may be present, with the need, however, to evaluate the potential effect of sharing a pollinator assemblage on reproductive success of both species.
Abstract: 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.
Abstract: Plant communities of soils naturally enriched in copper and cobalt in Katanga (D. R. Congo) are critically threatened in the short term due to mining activities. For biodiversity conservation and ecosystem restoration purposes, there is an urgent need to acquire more knowledge on those plant communities including their diversity and their relationships to environmental factors. The classification of 62 vegetation plots located in 6 metal-rich rocky hills in the Tenke Fungurume mining area resulted in 3 well-defined steppic and steppic savanna communities. Canonical analysis showed that the community comprising the largest proportion of strictly endemic metallophytes (i.e. species that only occur on metal-rich soils) developed in the soils with the most elevated concentrations of Cu and Co. However, contrasting species assemblages in the two other plant communities were explained by soil nutrients and percentage rocks in addition to heavy metal concentrations. The results of this study will assist with restoration efforts because they (1) provide a rigorous assessment of communities before a disturbance and (2) define essential edaphic conditions needed for the reestablishment of critical communities.
Abstract: Cu tolerance and accumulation have been studied in Haumaniastrum katangense, a cuprophyte from Katanga (DR Congo), previously described as a copper hyperaccumulator. Nicotiana plumbaginifolia, a well-known non-tolerant and non-accumulator species, was used as a control. The germination rate of H. katangense was enhanced by copper and fungicide addition, suggesting that fungal pathogens, which restrain germination in normal conditions, are limiting. In hydroponic culture in the Hoagland medium, H. katangense did not grow well, in contrast to N. plumbaginifolia. Better growth was achieved by adding fungicide or higher copper concentrations. The maximal non-effective concentration (NEC) was 12 µM CuSO4 for H. katangense grown in hydroponics, i.e. 24 times greater than Cu concentration in the Hoagland medium. By comparison, copper concentrations greater than 0.5 µM had a negative effect on the growth of N. plumbaginifolia. EC50 (50% effective concentration) in hydroponics was 40 µM CuSO4 for H. katangense and 6 µM CuSO4 for N. plumbaginifolia. EC100 (100% effective concentration) was 100 µM CuSO4 for H. katangense and 15 µM CuSO4 for N. plumbaginifolia. In soil, growth was also stimulated by Cu addition up to 300 mg kg-1 CuSO4. Surplus copper was also required for cultivating H. katangense in sterile conditions, suggesting that Cu excess may be necessary for needs other than pathogen defence. Cu accumulation in the shoot has been measured for N. plumbaginifolia and H. katangense at their respective NEC. Cu allocation in the two species showed a similar response to increasing Cu concentrations, i.e. root/shoot concentration ratio well above 1. In conclusion, H. katangense is highly tolerant to copper and has elevated copper requirement even in the absence of biotic interactions. Its accumulation pattern is typical of an excluder species.
Abstract: This study sought to determine the main genomic regions that control zinc (Zn) hyperaccumulation in Arabidopsis halleri and to examine genotype x environment effects on phenotypic variance. To do so, quantitative trait loci (QTLs) were mapped using an interspecific A. halleri x Arabidopsis lyrata petraea F(2) population. The F(2) progeny as well as representatives of the parental populations were cultivated on soils at two different Zn concentrations. A linkage map was constructed using 70 markers. In both low and high pollution treatments, zinc hyperaccumulation showed high broad-sense heritability (81.9 and 74.7%, respectively). Five significant QTLs were detected: two QTLs specific to the low pollution treatment (chromosomes 1 and 4), and three QTLs identified at both treatments (chromosomes 3, 6 and 7). These QTLs explained 50.1 and 36.5% of the phenotypic variance in low and high pollution treatments, respectively. Two QTLs identified at both treatments (chromosomes 3 and 6) showed significant QTL x environment interactions. The QTL on chromosome 3 largely colocalized with a major QTL previously identified for Zn and cadmium (Cd) tolerance. This suggests that Zn tolerance and hyperaccumulation share, at least partially, a common genetic basis and may have simultaneously evolved on heavy metal-contaminated soils.
Abstract: Background and aims - The occurrence of natural plant communities on Cu-enriched substrates over significant 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 field. Conservational status was established using IUCN criteria based on current and projected variation of population size and number.
Key results - Thirty-two taxa are identified as strict endemics of Cu-rich soil in Katanga, i.e. absolute metallophytes. Twenty-four of these are known from one to five localities only. Twenty-three other taxa are identified 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 insufficiently known. The low proportion of endemics (c. 5%) in the flora of Cu-rich soil in Katanga possibly indicates a recent origin of much of this flora. Arguments in favour of neoendemism and relictual endemism, respectively, are discussed briefly. 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 difficult 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 flora of Cu-rich soil in Katanga and should help prioritise future conservation efforts.
Abstract: 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.
Abstract: Cuprophytes are plants that mostly occur on Cu-rich soil in SC Africa. Crepidorhopalon perennis is endemic of a single site. C. tenuis has a broader niche, from normal to Cu-rich soil. Both have been considered as Cu-Co accumulators. We examined soil factors controlling heavy metal accumulation and plant fitness in natural populations. Plant mass and element concentrations in plants and soil were determined in 153 samples from five populations of C. tenuis on copper soil (CTC), two on normal soil (CTN) and the single population of C. perennis (CP). Soil in Cu-sites had higher concentrations of Ca, Mg, P, Mn, Zn, Cu, Co. Plants from Cu-sites were larger and had higher Cu and Co content, and lower Mg, Mn and Ca. Cu in shoots was influenced positively by Cu and Mn and negatively by Ca in the soil. Co in shoots was influenced positively by Co and negatively by Mn and Fe in the soil. Shoot mass was influenced positively by Cu and Mn (CT) or by Cu and Co (both species pooled) in the soil. The results suggest that C. tenuis and C. perennis are genuinely cuprophilous species. Large variation in metal accumulation in shoots can be accounted for by synergistic and antagonistic interactions among several heavy metals, yielding specific accumulation patterns in different populations.
Abstract: 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.
