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Plant and soil 475(1-2), 515 - 534 (2022). doi:10.1007/s11104-022-05388-3, PurposeThe Cunoniaceae are a major component of the New Caledonian flora with 91 endemic species that are highly unusual in that multiple metals are hyperaccumulated in different species. This makes it an ideal model system for studying the nature of the hyperaccumulation phenomenon.MethodsX-ray fluorescence spectroscopy (XRF) scanning of all herbarium collections of the Cunoniaceae was undertaken at the Herbarium of New Caledonia to reveal incidences of nickel (Ni) and manganese (Mn) accumulation. Following on, the Mn hyperaccumulating P. reticulata and the Ni hyperaccumulating P. xaragurensis were selected for detailed follow-up investigations using synchrotron-based X-ray fluorescence microscopy (XFM).ResultsThe systematic XRF screening of herbarium specimens showed that numerous species have high foliar Mn and Ni with species either accumulating Ni or Mn, but not both elements simultaneously. Soil ‘extractable’ Mn and Ni concentrations associated with Pancheria reticulata and P. xaragurensis greatly varies between the species. The XFM data shows that P. reticulata has a distinctive distribution pattern with Mn concentrated in large hypodermal cells. This contrasts with P. xaragurensis where Ni was mainly localized in and around the epidermis, and hypodermal cells were not observed., Published by Springer Science + Business Media B.V, Dordrecht [u.a.]

International audience; Conservation agriculture (CA) is one strategy with which both sustainability and productivity can be achieved by improving soil health. However, linkages between practices, soil health and cropping system performance remain poorly disentangled. We assessed the relationships between soil health and cropping system performance for three maize-based cropping systems in New Caledonia. Two CA systems, one with direct seeding into a mixed species dead mulch (CA-DM) and one into a stylo living mulch (CA-LM), were compared to a conventional tillage (CT) system. CA vs. CT experiment started in 2011, whereas the differentiation between CA-DM and CA-LM was initiated in 2017 only. In 2018, soil health was evaluated using Biofunctool (R), a set of ten in-field tools that assess soil carbon transformation, structure maintenance and nutrient cycling functions. The performance of the three cropping systems were assessed by monitoring weeds, maize growth and yield components. Structural equation modelling (SEM) was used to disentangle the links between agricultural management, soil health and cropping system performance. Soil structure maintenance and nutrient cycling functions were higher under CA-DM and CA-LM than under CT, and carbon transformation function was higher under CA-DM than under CT and CA-LM. Overall, the soil health index (SHI) was 1.3-fold higher under CA systems than under CT. Cropping system management had both direct and indirect effects on soil functioning and crop productivity leading to a 1.3-fold higher yield under CA than under CT. The direct and indirect effects of CA systems on soil health had positive impacts on ecosystem services (i.e., productivity, weed regulation and soil ecosystem services). Such integrative approaches that account for the relationships and possible trade-offs between cropping system components enable a better understanding of the effects and the performance of practices, and support adaptive agricultural management.

International audience

Simple Summary Fruit-piercing moths have long been cited as important pests in tropical and subtropical countries but genus as Eudocima, has recently gained in significance, and more specifically Eudocima phalonia (Linneaus). An overview of the current pest control proposed in the literature pointed the lack of sustainable integrated pest management. A synthesis of available data opens the research per-spectives that need to be encouraged in the ecological transition of our agricultural models. Abstract When referring to fruit-piercing moths, the genus Eudocima, and more specifically Eudocima phalonia (Linneaus), is cited as a worldwide crop pest. Damages associated with this pest are substantial on more than 100 fruit species, wherever it is encountered. In New Caledonia, the once occasional pest has become a serious threat to the current fruit arboriculture. Particularly devastating during outbreak periods, it has become an urgent need to find a suitable solution able to support farmers in the ecological transition of our agricultural models. This review proposes a synthesis of the existing data and publications on E. phalonia, worldwide and especially in New Caledonia, with recent observations. The assessment of this knowledge and the dynamics of the species in the territory of New Caledonia provide key information for a better prospect of adapted solutions.

The OCBIL theory comprises a set of hypotheses to comprehend the biota of old, climatically buffered, infertile landscapes (OCBILs). Here, we review evidence from the literature to evaluate the extent to which this theory could apply to the biodiversity hotspot of New Caledonia. We present geological, pedological and climatic evidence suggesting how the island might qualify as an OCBIL. The predictions of OCBIL theory are then reviewed in the context of New Caledonia. There is evidence for a high rate of micro-endemism, accumulation of relict lineages, a high incidence of dioecy, myrmecochory and nutritional specializations in plants. New Caledonian vegetation also exhibits several types of monodominant formations that reveal the importance of disturbances on the island. Fires and tropical storms are likely to be important factors that contribute to the dynamic of New Caledonian ecosystems. Although naturally infertile, there is archaeological evidence that humans developed specific horticultural practices in the ultramafic landscapes of New Caledonia. Further comparisons between New Caledonia and other areas of the world, such as South Africa and Southwest Australia, are desirable, to develop the OCBIL theory into a more robust and generalized, testable framework and to determine the most efficient strategies to preserve their outstanding biodiversity.

Species distribution models (SDMs) represent a widely acknowledged tool to identify priority areas on the basis of occurrence data and environmental factors. However, high levels of topographical and climatic micro-variation are a hindrance to reliably modelling the distribution of narrow-endemic species when based on classic occurrence and climate datasets. Here, we used high-resolution environmental variables and occurrence data obtained from dedicated field studies to produce accurate SDMs at a local scale. We modelled the potential current distribution of 23 of the 25 rarest species from Mount Kaala, a hotspot of narrow-endemism in New Caledonia, using occurrence data from two recent sampling campaigns, and eight high-resolution (10 m and 30 m) environmental predictors in a Species Distribution Modelling framework. After a first sampling operation, we surveyed six additional areas containing, overall, 13 of the 20 species modelled at this stage, to validate our projections where the highest species richness levels were predicted. The ability of our method to define conservation areas was largely validated with an average 84% of predicted species found in the validation areas, and additional data collected enabling us to model three more species. We therefore identified the areas of highest conservation value for the whole of Mount Kaala. Our results support the ability of SDMs based on presence-only data such as MaxEnt to predict areas of high conservation value using fine-resolution environmental layers and field-collected occurrence data in the context of small and heterogeneous systems such as tropical islands.

International audience; The genetic basis and evolution of sex determination in dioecious plants is emerging as an active area of research with exciting advances in genome sequencing and analysis technologies. As the sole species within the sister lineage to all other extant flowering plants, Amborella trichopoda is an important model for understanding the evolution and development of flowers. Plants typically produce only male or female flowers, but sex determination mechanisms are unknown for the species. Sequence data derived from plants of natural origin and an F1 mapping population were used to identify sex-linked genes and the nonrecombining region. Amborella trichopoda has a ZW sex determination system. Analysis of genes in a 4 Mb nonrecombining sex-determination region reveals recent divergence of Z and W gametologs, and few Z- and W-specific genes. The sex chromosomes of A. trichopoda evolved less than 16.5 Myr ago, long after the divergence of the extant angiosperms.

Sex determination is poorly understood in plants. Amborella trichopoda is a well-known plant model for evo-devo studies, which is also dioecious (has male and female individuals), with an unknown sex determination mechanism. A. trichopoda is a “sex switcher”, which points to possible environmental factors that act on sex, but populations grown from seed under greenhouse conditions exhibit a 50:50 sex ratio, which indicates the operation of genetic factors. Here, we use a new method (SDpop) to identify sex-linked genes from genotyping data of male and female individuals sampled in the field, and find that A. trichopoda has a ZW sex-chromosome system. The sex-linked genes map to a 4 Mb sex-determining region on chromosome 9. The low extent of ZW divergence suggests these sex chromosomes are of recent origin, which is consistent with dioecy being derived character in the A. trichopoda lineage. Our work has uncovered clearly formed sex chromosomes in a species in which both genetic and environmental factors can influence sex.One Sentence SummaryAmborella trichopoda, a dioecious species in which both genetics and the environment influence sex, possesses a pair of quite recently evolved ZW chromosomes.

The identification and use of hyperaccumulator plants in mining projects has been recognized as an important component of life of mine planning at several sites around the world. Mine planning that includes hyperaccumulator plants requires operators to maximize the biological resources of a site by discovering and utilizing these unusual plant species at the early stages of a mine’s development. These locally adapted hyperaccumulator species can then be used for rehabilitation in and around the mine area or be utilised for their potential to extract ecocatalysts and metals. These opportunities should be more widely explored so that these unique plants can become an integrated and valuable part of the mining process. This chapter concentrates on the experiences of integrating hyperaccumulating plants into mine rehabilitation projects in Indonesia and New Caledonia to highlight some of the opportunities and challenges encountered when attempting to incorporate these species into the mining cycle.

Background and Aims Hybanthus austrocaledonicus (Violaceae) is a nickel (Ni) hyperaccumulator endemic to New Caledonia. One of the specimens stored at the local herbarium had a strip of bark with a remarkably green phloem tissue attached to the sheet containing over 4 wt% Ni. This study aimed to collect field samples from the original H. austrocaledonicus locality to confirm the nature of the green ‘nickel-rich phloem’ in this taxon and to systematically assess the occurrence of Ni hyperaccumulation in H. austrocaledonicus and Hybanthus caledonicus populations. Methods X-ray fluorescence spectroscopy scanning of all collections of the genus Hybanthus (236 specimens) was undertaken at the Herbarium of New Caledonia to reveal incidences of Ni accumulation in populations of H. austrocaledonicus and H. caledonicus. In parallel, micro-analytical investigations were performed via synchrotron X-ray fluorescence microscopy (XFM) and scanning electron microscopy with X-ray microanalysis (SEM-EDS). Key Results The extensive scanning demonstrated that Ni hyperaccumulation is not a characteristic common to all populations in the endemic Hybanthus species. Synchrotron XFM revealed that Ni was exclusively concentrated in the epidermal cells of the leaf blade and petiole, conforming with the majority of (tropical) Ni hyperaccumulator plants studied to date. SEM-EDS of freeze-dried and frozen-hydrated samples revealed the presence of dense solid deposits in the phloem bundles that contained >8 wt% nickel. Conclusions The occurrence of extremely Ni-rich green phloem tissues appears to be a characteristic feature of tropical Ni hyperaccumulator plants.

New Caledonia is a global biodiversity hotspot known for its metal hyperaccumulator plants. X-ray fluorescence technology (XRF) has enabled non-destructive and quantitative determination of elemental concentrations in herbarium specimens from the ultramafic flora of the island. Specimens belonging to six major hyperaccumulator families (Cunoniaceae, Phyllanthaceae, Salicaceae, Sapotaceae, Oncothecaceae and Violaceae) and one to four specimens per species of the remaining ultramafic taxa in the herbarium were measured. XRF scanning included a total of c. 11 200 specimens from 35 orders, 96 families, 281 genera and 1484 species (1620 taxa) and covered 88.5% of the ultramafic flora. The study revealed the existence of 99 nickel hyperaccumulator taxa (65 known previously), 74 manganese hyperaccumulator taxa (11 known previously), eight cobalt hyperaccumulator taxa (two known previously) and four zinc hyperaccumulator taxa (none known previously). These results offer new insights into the phylogenetic diversity of hyperaccumulators in New Caledonia. The greatest diversity of nickel hyperaccumulators occur in a few major clades (Malphigiales and Oxalidales) and families (Phyllanthaceae, Salicaceae, Cunoniaceae). In contrast, manganese hyperaccumulation is phylogenetically scattered in the New Caledonian flora.

Plant and soil 457(1-2), 293 - 320 (2020). doi:10.1007/s11104-020-04714-x, AimsThis study aimed to establish elemental profiles and to spatially resolve the elemental distribution in five New Caledonian woody Ni hyperaccumulator plant species (Geissois pruinosa var. pruinosa, Homalium francii, Hybanthus austrocaledonicus, Psychotria gabriellae, and Pycnandra acuminata) originating from the Cunoniaceae, Salicaceae, Violaceae, Rubiaceae, and Sapotaceae families respectively.MethodsUsing synchrotron-based micro-X-ray Fluorescence (��XRF) imaging of different plant tissues, from the roots to the shoots and reproductive organs, this study aimed to clarify how distribution patterns of nickel, and other physiologically relevant elements, differ between these species.ResultsThe results show that the tissue-level and cellular-level distribution of nickel in P. gabriellae, H. austrocaledonicus, G. pruinosa var. pruinosa, and H. francii conform with the majority of studied Ni hyperaccumulator plant species globally, including (temperate) herbaceous species, with localization mainly in epidermal cells and phloem bundles. However, P. acuminata has nickel-rich laticifers, which constitute an independent network of cells that is parallel to the vascular bundles and are the main sink for nickel.ConclusionsSynchrotron-based micro-X-ray Fluorescence (��XRF) is a powerful method for investigating how metal hyperaccumulation influences acquisition and spatial distribution of a wide range of elements. This non-invasive method enables investigation into the in vivo distribution of multiple elements and the structure and organisation of cells (e.g. laticifers)., Published by Springer Science + Business Media B.V, Dordrecht [u.a.]

International audience; The Anthropocene epoch is associated with the spreading of metals in the environment increasing oxidative and genotoxic stress on organisms. Interestingly, about 500 plant species growing on metalliferous soils acquired the capacity to accumulate and tolerate tremendous amount of nickel in their shoots. The wide phylogenetic distribution of these species suggests that nickel hyperaccumulation evolved multiple times independently. However, the exact nature of these mechanisms and whether they have been recruited convergently in distant species is not known. To address these questions, we have developed a cross-species RNA-Seq approach combining differential gene expression analysis and cluster of orthologous group annotation to identify genes linked to nickel hyperaccumulation in distant plant families. Our analysis reveals candidate orthologous genes encoding convergent function involved in nickel hyperaccumulation, including the biosynthesis of specialized metabolites and cell wall organization. Our data also point out that the high expression of IREG/Ferroportin transporters recurrently emerged as a mechanism involved in nickel hyperaccumulation in plants. We further provide genetic evidence in the hyperaccumulator Noccaea caerulescens for the role of the NcIREG2 transporter in nickel sequestration in vacuoles. Our results provide molecular tools to better understand the mechanisms of nickel hyperaccumulation and study their evolution in plants.

International audience; Amborella trichopoda (Amborellaceae) is a shrub endemic to New Caledonia in the Southwest Pacific region. This plant suddenly became famous when molecular phylogenetic studies revealed that this sole species is likely the sister taxon to all other angiosperms. It has thus been a prime research model for reconstructing plant evolution and gaining insight into what the earliest angiosperms looked like. A wealth of studies on Amborella have now shed considerable light on its genome, morphology, anatomy, physiology, development, and architecture – this research is reviewed in this article. While Amborella likely retained some ancestral traits, critical character reconstructions have also highlighted some derived and sometimes unique characters in this species. The history of Amborella is also tied to the South Pacific archipelago of New Caledonia, its homeland. It was part of the New Caledonian biogeography puzzle and its genetic history shed light on the dynamics of its ecosystem, the rainforest understorey. Amborella is now cultivated in botanical gardens and has been the focus of some conservation measures that will also benefit other species in this biodiversity hotspot.

The Anthropocene epoch is associated with the spreading of metals in the environment increasing oxidative and genotoxic stress on living organisms1,2. Once regarded as a curiosity, plants hyperaccumulating metals are now envisioned as an opportunity to remediate metal contaminated soils. About 500 plant species adapted to metalliferous soils acquired the capacity to hyperaccumulate (>0.1% of dry weight) nickel in their shoot3. The phylogenetic distribution of these hyperaccumulators in 50 families suggest that this complex trait evolved multiple times independently from basic mechanisms involved in metal homeostasis. However, the exact nature of these mechanisms and whether they are shared between various lineages is not known. Here, using cross-species transcriptomic analyses in different plant families, we have identified convergent functions that may represent major nodes in the evolution of nickel hyperaccumulation. In particular, our data point out that constitutive high expression of IREG/Ferroportin transporters recurrently emerged as a mechanism involved in nickel hyperaccumulation.

International audience; The biodiversity hotspot of New Caledonia hosts high levels of endemism (74% of flora) that is threatened increasingly by climate change, habitat reduction, and inva-sive species. The fruit-eating red-vented bulbul (Pycnonotus cafer) is currently invading the main island of the archipelago, and its recent dispersal out of urbanized habitats raises questions about its potential to disperse noxious plant seeds along urban corridors and beyond. Indeed, the red-vented bulbul is considered a vector of several introduced plant species in its alien range including Miconia calvescens, Lantana camara, and Schinus terebinthifolius. We conducted a quantitative assessment of the bulbul's fruits consumption by analyzing the gut contents of shot birds. We estimated gut passage times for four species of fruit found in gut contents (S. terebin-thifolius, Myrtastrum rufopunctatum, Passiflora suberosa, and Ficus prolixa) and tested the effects of bird digestion on seed germination rates for two species. Finally, we monitored the movements of individual VHF radio-tagged red-vented bulbuls. All of the consumed fruit species we identified here have red fleshy diaspore, including fruit of the shrub M. rufopunctatum that occurred frequently (9.6%) in bulbul gut samples. Median gut passage times were short (15-41 min), corresponding to short-distance seed transportation (77-92 m). The effect of gut passage was positive for the germination of the invasive S. terebinthifolius and negative for the endemic M. ru-fopunctatum, suggesting a potential bias in the contribution to the dispersal toward alien species. This study provides the first integrated assessment of mechanisms involved in the seed dispersal effectiveness of this high-concern invasive bird species that is expected to face similar plant communities in most of its alien range in tropical islands. More generally, our results enhance knowledge of synergies between non-native frugivores and plant species dispersal.

International audience

The Anthropocene epoch is associated with the spreading of metals in the environment increasing oxidative and genotoxic stress on living organisms. Metalliferous soils such as serpentine can host peculiar plants called hyperaccumulators due to their capacity to accumulate tremendous amount of metal in their shoot (e.g. >0.1% of dry weight for nickel). Once regarded as a curiosity, plants hyperaccumulating metals are now envisioned as an opportunity to remediate metal contaminated soils. The wide phylogenetic distribution of nickel hyperaccumulators (~500 species) suggest that this complex trait evolved multiple times independently from the dysregulation of basic mechanisms involved in metal homeostasis including metal chelation, transport and oxidative stress responses. However, the exact nature of these mechanisms and whether the same molecular mechanisms have been recruited convergently to reach this extreme trait is not known. To address these questions, we developed a comparative cross-species RNA-Seq approach combining differential gene expression analysis and cluster of orthologous group annotation. This analysis reveals candidate orthologous genes encoding convergent function, including the biosynthesis of histidine and flavonoids, involved in nickel hyperaccumulation. Our data also point out that the constitutive high expression of IREG/Ferroportin transporters recurrently emerged as a mechanism involved in nickel hyperaccumulation in a wide diversity of plant families. We further provide genetic evidence in the hyperaccumulator Noccaea caerulescens that IREG/Ferroportin transporters are involved in nickel sequestration in vacuoles. This study paves the way for comparative approaches to identify molecular mechanisms involved in metal hyperaccumulation in a wide diversity of plant species.

The identification and use of hyperaccumulator plants in mining projects has been recognised as an important component part of mine planning at several sites around the world. Indeed, mine planning that includes hyperaccumulator plants requires operators to maximize the biological resources of a site by discovering and utilizing these unusual plant species at the early planning stages. These locally adapted hyperaccumulator species can then be used for rehabilitation in and around the mine area, or be utilized for their potential to extract ecocatalysts and metals. Such opportunities should be more widely explored so that these unique plants can become an integrated and valuable part of the mining process. This chapter concentrates on the experiences of integrating hyperaccumulating plants into mine rehabilitation projects in Indonesia and New Caledonia, in order to highlight some of the opportunities and challenges encountered when attempting to incorporate these species into the mining cycle.

International audience; Desiccation tolerance allows plant seeds to remain viable in a dry state for years and even centuries. To reveal potential evolutionary processes of this trait, we have conducted a shotgun proteomic analysis of isolated embryo and endosperm from mature seeds of Amborella trichopoda, an understory shrub endemic to New Caledonia that is considered to be the basal extant angiosperm. The present analysis led to the characterization of 415 and 69 proteins from the isolated embryo and endosperm tissues, respectively. The role of these proteins is discussed in terms of protein evolution and physiological properties of the rudimentary, underdeveloped, Amborella embryos, notably considering that the acquisition of desiccation tolerance corresponds to the final developmental stage of mature seeds possessing large embryos.

International audience

International audience; New Caledonia is a widely recognised marine and terrestrial biodiversity hot spot. However, this unique environment is under increasing anthropogenic pressure. Major threats are related to land cover change and include fire, urban sprawling and mining. Resulting habitat loss and fragmentation end up in serious erosion of the local biodiversity. Mining is of particular concern due to its economic significance for the island. Open cast mines were exploited there since 1873, and scraping out soil to access ores wipes out flora. Resulting perturbations on water flows and dramatic soil erosion lead to metal-rich sediment transport downstream into rivers and the lagoon. Conflicting environmental and economic aspects of mining are discussed in this paper. However, mining practices are also improving, and where impacts are inescapable ecological restoration is now considered. Past and ongoing experiences in the restoration of New Caledonian terrestrial ecosystems are presented and discussed here. Economic use of the local floristic diversity could also promote conservation and restoration, while providing alternative incomes. In this regard, Ecocatalysis, an innovative approach to make use of metal hyperaccumulating plants, is of particular interest.

Efficient in situ and ex situ conservation strategies are urgently needed in biodiversity hotspots, where high concentrations of endemic plant species are undergoing exceptional loss of habitat. In particular, determining seed desiccation sensitivity is a key prerequisite to design storage methods useful for ex situ programs. In this study, we explored seed desiccation sensitivity and its link with phenological and morphological traits as well as with the environmental variables for 45 New Caledonian plant species. Desiccation sensitivity was quantified through RH50, that is, the relative humidity at which 50% of initial viable seeds died. RH50 was found to be positively associated with the initial seed water content, seed mass, precipitation seasonality, precipitation of the warmest quarter, and presence in rainforest habitats. In contrast, the ability of species to endure desiccation increased in drier habitats such as dry forest. We also found that desiccation sensitivity was consistent at the genus level. These new data provide the basis to establish conservation plans for a large array of plant species in New Caledonia. Moreover, this study may help us to better understand the underlying mechanisms of desiccation sensitivity and to predict desiccation sensitivity of other taxa within the New Caledonian flora on the basis of taxonomy, functional traits and environmental features.

Background and aims Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda , the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade. Methods Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms. Key results Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth. Conclusions Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.

Background and Aims This work aimed to gain insight into the breeding system at the base of living angiosperms through both character state reconstructions and the study of sex ratios and phenotypes in the likely sister to all other living angiosperms, Amborella trichopoda . Methods Sex phenotypes were mapped onto a phylogeny of basally diverging angiosperms using maximum parsimony. In parallel, sex ratios and phenotypes were studied over two consecutive flowering seasons in an ex situ population of A. trichopoda , while the sex ratio of an in situ population was also assessed. Key Results Parsimony analyses failed to resolve the breeding system present at the base of living angiosperms, but indicated the importance of A. trichopoda for the future elucidation of this question. The ex situ A. trichopoda population studied showed a primary sex ratio close to 1:1, though sex ratio bias was found in the in situ population studied. Instances of sexual instability were quantified in both populations. Conclusions Sex ratio data support the presence of genetic sex determination in A. trichopoda , whose further elucidation may guide inferences on the breeding system at the base of living angiosperms. Sexual instability in A. trichopoda suggests the operation of epigenetic mechanisms, and the evolution of dioecy via a gynodioecious intermediate.

The tropical shrub Beauprea was already present in Gondwana when Zealandia drifted away from Antarctica 82 million years ago., New Caledonia and New Zealand belong to the now largely submerged continent Zealandia. Their high levels of endemism and species richness are usually considered the result of transoceanic dispersal events followed by diversification after they re-emerged from the Pacific Ocean in the mid-Cenozoic. We explore the origin and evolutionary history of Beauprea (Proteaceae), which is now endemic to New Caledonia but was once spread throughout eastern Gondwana, including New Zealand. We review the extensive Beauprea-type pollen data in the fossil records and analyze the relationship of these fossil taxa to extant genera within Proteaceae. We further reconstruct the phylogenetic relations among nine extant species of Beauprea and estimate the age of the Beauprea clade. By incorporating extinct taxa into the Beauprea phylogenetic tree, we reconstruct the ancient distribution of this genus. Our analysis shows that Beauprea originated c. 88 Ma (million years ago) in Antarctica–Southeastern Australia and spread throughout Gondwana before its complete breakup. We propose that Beauprea, already existing as two lineages, was carried with Zealandia when it separated from the rest of Gondwana c. 82 Ma, thus supporting an autochthonous origin for Beauprea species now in New Caledonia and historically in New Zealand up to 1 Ma. We show that the presence of Beauprea through transoceanic dispersal is implausible. This means that neither New Caledonia nor New Zealand has been entirely submerged since the Upper Cretaceous; thus, possible vicariance and allopatry must be taken into account when considering the high levels of endemism and species richness of these island groups.

We developed ten microsatellites markers to study the population genetic structure of two ultramafic scrublands species in New Caledonia, Scaevola montana a common species used in ecological restoration of mining sites, and S. coccinea a narrow endemic species of the Tontouta valley. The markers were isolated from S. montana. Nine loci are polymorphic in S. montana; eight were polymorphic in S. coccinea. The narrow endemic species showed lower variation at these loci than S. montana. There is a significant heterozygosity deficit in S. montana at four loci, and a global significant inbreeding coefficient across all loci (F IS = 0.159). In contrast, the tested populations of S. coccinea did not show significant deviations from Hardy–Weinberg expectations. These markers are now being used in conservation genetic studies aiming to understand the biology of these species and to provide information to guide restoration programmes.

It is generally assumed that there is a good correlation between systematics and the secondary compounds found in plants. However because of the frequent homoplasy of chemical characters this has been difficult to test using statistical methods. Here we applied two nonparametric tests on a published data set, where 50 species of New Caledonian Cunoniaceae were screened for bioactivity against several pathogenic strains. Using Moran's I index we showed that in two of nine tests against pathogenic strains there was a significantly higher similarity than expected in bioactivities between species belonging to the same genus and a significantly higher than expected dissimilarity in bioactivity between species belonging to different tribes. When considering the bioactivities against all pathogenic strains with Mantel tests, we also found significant correlation between bioactivity and phylogenetic distance in two of four tests. This has implications in screening and conservation. Searches for new molecules and bioactivity should preferentially be made on species spread across the tree of life. There is also a need to preserve as much phylogenetic diversity as possible to make sure that the widest reservoir of natural compounds remains available for future generations.

International audience; Relationships between the trace-elements (TE) content of plants and associated soil have been widely investigated especially to understand the ecology of TE hyperaccumulating species to develop applications using TE phytoextraction. Many studies have focused on the possibility of quantifying the soil TE fraction available to plants, and used bioconcentration (BC) as a measure of the plants ability to absorb TE. However, BC only offers a static view of the dynamic phenomenon of TE accumulation. Accumulation kinetics are required to fully account for TE distributions in plants. They are also crucial to design applications where maximum TE concentrations in plant leaves are needed. This paper provides a review of studies of BC (i.e. soil-plant relationships) and leaf-age in relation to TE hyperaccumulation. The paper focuses of Ni and Mn accumulators and hyperaccumulators from New Caledonia who were previously overlooked until recent Ecocatalysis applications emerged for such species. Updated data on Mn hyperaccumulators and accumulators from New Caledonia are also presented and advocate further investigation of the hyperaccumulation of this element. Results show that leaf-age should be considered in the design of sample collection and allowed the reclassification of Grevillea meisneri known previously as a Mn accumulator to a Mn hyperaccumulator.

International audience; Increasing pressure on mineral resources has drawn research efforts into innovative supply and recycling. Metal-rich biomass produced in phytoextraction recently proved an interesting starting material for green chemistry. It allows the production of new catalysts, referred to as ecocatalysts. Ecocatalysts provide increased yields in chemical production and increased regio- and chemo-selectivity, which result in high added value. This new approach to using metal-rich biomass could spur the development of phytoextraction, a technique considered promising for long, yet without credible economic outlets. In this regard, metallophyte biodiversity hotspots, such as New Caledonia, are of particular interest for biomass supply. Potential phytoextraction from mine spoils using two species endemic to New Caledonia is discussed here. Geissois pruinosa, a hypernickelophore, and Grevillea exul, a Mn accumulator, were selected for these original experiments. The results presented here 20 months after plantation of young trees from a nursery show the interest of the approach. Mean Ni concentrations of up to 1513 mg kg−1 are reported in G. pruinosa, as well as 2000 mg kg−1 Mn in G. exul. Concentrations of Ni and Mn in the leaves of each species appear to be correlated with leaf age. Plantation of these species may also ensure mine reclamation, and experiments were conducted with the principles of ecological restoration in mind adding a further dimension to the approach.

International audience; Phytomining technology employs hyperaccumulator plants to take up metal in harvestable plant biomass. Harvesting, drying and incineration of the biomass generates a high-grade bio-ore. We propose that ``agromining'' (a variant of phytomining) could provide local communities with an alternative type of agriculture on degraded lands; farming not for food crops, but for metals such as nickel (Ni). However, two decades after its inception and numerous successful experiments, commercial phytomining has not yet become a reality. To build the case for the minerals industry, a large-scale demonstration is needed to identify operational risks and provide ``real-life'' evidence for profitability.

International audience; Cunoniaceae are represented in New Caledonia by some 90 species, all of them endemic, and the family is thus a significant element in this diverse island flora. We present a descriptive survey of floral biology for the seven genera present, covering floral structure and colour, inflorescence shape, sexual system and phenology, plus details of floral visitors, where known, based on field observations; individual records of potential pollinators are tabulated in appendices. The flowers are polysymmetric (or almost so) and provide nectar and/or pollen as floral rewards. Two genera are dioecious and some species are mass flowering. Generalist entomophily is associated with several floral syndromes although the introduction of Apis mellifera has partially obscured historic relationships between some Cunoniaceae and their insect-pollinators. Codia and Pancheria both have sweetly scented, often creamish, spherical capitula and their floral visitors include honey bees, beetles, flies and native bees, especially halictids. Spiraeanthemum and Hooglandia have small, often whitish flowers in paniculate inflorescences but data on potential pollinators are few. Racemes occur in Weinmannia (flowers white, apparently scentless) and Cunonia p.p. (flowers white, pink or reddish with a faint foetid odour); visitors are mostly honey bees, plus ants, butterflies and native bees, and occasionally birds in the case of two reddish-flowered species. Ornithophily occurs in Geissois (flowers red, scentless, in bottle-brush racemes) and Cunonia macrophylla (flowers yellow-green, in one-sided racemes); their floral visitors are commonly Meliphagidae plus some Psittacidae and Zosteropidae. Pteropodid bats are also occasional visitors to Geissois. Geckos have been reported as flower-visitors in two genera though their contribution to pollen transfer is likely to be sporadic at most. Topics that require further investigation include some details of floral biology and the floral cycle, and the possible adaptive significance of different inflorescence shapes. Unanswered questions include: What visits taxa with paniculate inflorescences?, and for all genera: Which types of floral visitor are the most efficient pollinators? For the family as a whole, generalist entomophily appears to be the ancestral mode of pollen transfer and morphological specialisations to ornithophily have occurred independently in two groups of species and possibly in a third. Our data on birds and geckos agree with a known trend for these types of floral visitation and pollination to be well developed on islands, and flower-visiting by lizards in New Caledonia is likely to be more common than has been documented so far, both in Cunoniaceae and in the flora as a whole.

Plants growing on serpentine soils are usually assumed to be nickel (Ni)-tolerant species. The objective of the work reported here was to find out whether Cunonia macrophylla Brongniart & Gris, an endemic species common on Ni-rich soils in New Caledonia, is indeed Ni tolerant. In a greenhouse experiment, plants were watered with solutions containing Ni chloride (5 to 1000 mg Ni L−1) for 15 months before their morphological characteristics were measured, and the levels of nitrate, protein, and nutrients in the plants were determined. The plants grown with 5, 10, 50, and 100 mg Ni L−1 had more leaves, and there was a tendency toward greater stem thickness and fresh shoot biomass at 50 mg Ni L−1. Manganese (Mn), copper (Cu), and zinc (Zn) concentrations were also higher in the presence of 50 mg Ni L−1. One thousand mg Ni L−1 induced symptoms of Ni toxicity, and this effect may account for the lower concentration of potassium (K) in the shoots and roots of plants exposed to this concentration, as wel...

Le projet ECOMINE BIOTOP est centré sur le fonctionnement des topsoils et leur gestion lors de l’exploitation minière. Il propose à la fois des petit Poum - Verse Fredoexpérimentations sur le terrain, des travaux de recherche in situ et des expérimentations en serre et en laboratoire sur les topsoils, la caractérisation et le suivi de la banque de graines, l’activité microbienne, le potentiel mycorhizogène et son amélioration par inoculation. Les résultats obtenus permettent d’améliorer la gestion et l’utilisation des topsoils miniers néocalédoniens. Une étude sur la maîtrise de la diversité génétique des espèces végétales complète le projet. Ce programme aboutira à des recommandations pratiques sur les méthodes de gestion du topsoil, de mycorhizogène des plantes, de l’activité microbienne et de gestion de l’activité microbienne et de la dynamique des métaux en relation avec l’activité microbienne pour la restauration écologique après exploitation minière. Ce programme aboutit à des recommandations pratiques sur l’utilisation et la gestion du topsoil dans une optique de restauration écologique.

Some species of the Cunoniaceae are reputed to possess medicinal properties. An investigation of 50 species of this family in New Caledonia has permitted the screening of 204 extracts (101 ethyl acetate extracts and 103 methanol extracts) for antimicrobial activities against one yeast (Candida albicans), one filamentous fungus (Fusarium oxysporum), and eight bacterial species (Erwinia carotovora, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Corynebacterium accolans, Bacillus subtilis). Ninety‐six per cent of the plants exhibited antimicrobial activity, with a significant difference in the number of responses between fungi (18.8%) and bacteria (81.2%). Moreover, Gram +ve strains appear more sensitive than Gram ‐ve ones. The most active plants were Acsmithia meridionalis, A. pedunculata, Cunonia macrophylla, C. vieillardii, Pancheria alaternoides, and P. elegans. Cunonia macrophylla appears to be the best candidate for a chemica...

International audience; Two-hundred-and-four extracts (101 ethyl acetate extracts and 103 methanol extracts) from 50 species of Cunoniaceae from New Caledonia were screened for antioxidant properties due to free radical scavenging and/or xanthine oxidase (XOD) inhibitory activity. Of the crude extracts, 95.1% were active at a concentration of 50 mg/ml. Fifteen (27.8%) extracts showed more than 50% activity at 10 mg/ml and were studied for XOD inhibition. All were active against XOD at 50 mg/ml but only 6 (40%) showed up to 60% inhibition. Ethyl acetate extracts from the bark of Weinmannia dichotoma Brongniart & Gris, Weinmannia monticola Däniker and Cunonia lin-earisepala (Guillaumin) Bernardi and from the roots of Codia incrassata Pampanini, as well as methanol extract from the bark of Pancheria brunhesii Pampanini, exhibited the highest activities (between 70% and 86% XOD inhibition at 50 mg/ml). In view of these preliminary results, New Caledonian Cunoniaceae species appears to be promising material for the isolation of bioactive compounds.

Premise of the study: High-throughput sequencing of genomic DNA can recover complete chloroplast genome sequences, but the sequence data are usually dominated by sequences from nuclear/mitochondrial genomes. To overcome this deficiency, a simple enrichment method for chloroplast DNA from small amounts of plant tissue was tested for eight plant species including a gymnosperm and various angiosperms. Methods: Chloroplasts were enriched using a high-salt isolation buffer without any step gradient procedures, and enriched chloroplast DNA was sequenced by multiplexed high-throughput sequencing. Results: Using this simple method, significant enrichment of chloroplast DNA-derived reads was attained, allowing deep sequencing of chloroplast genomes. As an example, the chloroplast genome of the conifer Callitris sulcata was assembled, from which polymorphic microsatellite loci were isolated successfully. Discussion: This chloroplast enrichment method from small amounts of plant tissue will be particularly useful for studies that use sequencers with relatively small throughput and that cannot use large amounts of tissue (e.g., for endangered species).