Tanguy Jaffré

The relation between nickel and citric acid in some nickel-accumulating plants

Abstract A strong correlation has been found between the levels of nickel and citric acid in the leaves of 17 New Caledonian plant species which show a range of nickel-accumulating ability: Sebertia acuminata, Psychotria douarrei, Geissois pruinosa, Hybanthus austrocaledonicus, Hybanthus caledonicus, and 12 species of Homalium. Purified extracts of these plants contain nickel as a citrate complex. Three nickel-accumulating plants from beyond New Caledonia (Alyssum bertolonii, Alyssum serpyllifolium s.sp. lusitanicum and Pearsonia metallifera) do not contain unusually high levels of citrate, nor is citrate present in purified nickel-containing extracts of these species.

Phylogenetic relationships within Araucariaceae based on rbcL gene sequences

Phylogenetic relationships were determined in the Araucariaceae, which are now found mainly in the Southern Hemisphere. This conifer family was well diversified and widely distributed in both hemispheres during the Mesozoic era. The sequence of 1322 bases of the rbcL gene of cpDNA was determined from 29 species of Araucariaceae, representing almost all the species of the family. Phylogenetic trees determined by the parsimony method indicate that Araucariaceae are well defined by rbcL sequences and also that the monophyly of Agathis or Araucaria is well supported by high bootstrap values. The topology of these trees revealed that Wollemia had derived prior to Agathis and Araucaria. The rbcL phylogeny agrees well with the present recognition of four sections within Araucaria: Araucaria, Bunya, Eutacta, and Intermedia. Morphological characteristics of the number of cotyledons, position of male cone, and cuticular micromorphologies were evaluated as being phylogenetically informative. Section Bunya was found to be derived rather than to be the oldest taxon. Infrageneric relationships of Agathis could not be well elucidated because there are few informative site changes in the rbcL gene, suggesting the more recent differentiation of the species as their fossil records indicate. The New Caledonian Araucaria and Agathis species each formed a monophyletic group with very low differentiation in rbcL sequences among them, indicating rapid adaptive radiation to new edaphic conditions, i.e., ultramafic soils, in the post-Eocene era.

Isolation and identification of a citrato-complex of nickel from nickel-accumulating plants

Abstract An organometallic complex of nickel has been isolated from nickel-accumulating plants of New Caledonia and has been identified by a combination of infrared spectroscopy, high-voltage paper electrophoresis, gas-liquid chromatography and mass spectrometry. Most of the nickel in Sebertia acuminata, Homalium francii, Homalium guillainii, Homalium kanaliense, Hybanthus austrocaledonicus and Hybanthus caledonicus is found as a negatively-charged citratonickelate (II) complex with Ni(H 2 O) 6 2+ as the major cationic constituent.

Threatened plants of New Caledonia: Is the system of protected areas adequate?

With 76% of its 3063 native species of flora endemic, the New Caledonia biodiversity hotspot has long been recognized as having a high potential for conservation. Under the new IUCN Red List categories, 25% of the endemic plants are at risk (Conservation Dependent, Vulnerable, Endangered, Critically Endangered), and five species are already extinct. A review of their distribution demonstrates that 83% of the threatened species do not occur at all in a conservation area, and only 11% have their conservation status improved by a protected area. The protected area network is geographically and floristically very unbalanced, with the rainforest and high altitude maquis in the south concentrating most of the conservation effort. Conversely, the middle and northern segments of the island, as well as all of the dry west coast, are left without adequate conservation area. Two vegetation types, the sclerophyll forest and the unique low/middle altitude maquis, are virtually totally unprotected. We conclude that the current network of protected areas needs to be considerably expanded, in terms of both geographical/floristic subregions within New Caledonia and vegetation type covered. With only 54% of the conservation area covered by strict mining restrictions, existing reserves need to have their conservation efficiency improved by a more vigorous enforcement of their status, and by extending mining bans to all of them.

Identifying the early genetic consequences of habitat degradation in a highly threatened tropical conifer, Araucaria nemorosa Laubenfels

The early genetic effects of habitat degradation were investigated in the critically endangered conifer Araucaria nemorosa. This species occurs in New Caledonia, a global biodiversity hotspot where the worlds greatest concentration of endemic conifer species coincides with an extremely high level of habitat destruction due to fire and mining. Using seven microsatellite loci, estimates were made of genetic marker variation, inbreeding coefficients and population differentiation of adult and seedling cohorts of A. nemorosa. These were contrasted with equivalent estimates, made over similar spatial scales and with the same marker loci, in the locally common and more widespread sister species Araucaria columnaris. There were no significant differences in population genetic parameters between adult populations of the two species, despite their different abundances. However, in A. nemorosa, the juvenile cohort showed a loss of rare alleles and elevated levels of inbreeding when compared to the adult cohort. These genetic differences between the cohorts were not observed in the locally common A. columnaris. This suggests that recent environmental degradation is influencing the genetic structure of A. nemorosa populations. Although this is not detectable among predisturbance adult populations, an early warning of these impacts is evident in more recently established seedling cohorts. The conservation implications of these results are discussed.

Plant extinction in New Caledonia: protection of sclerophyll forests urgently needed

The sclerophyll forests which once extended over the lowlands of the west coast of New Caledonia are now reduced to small fragments representing about 2% (10 000 ha) of their original area. Much of the remaining forests are degraded. Threats to sclerophyll forests come from land clearance, grazing by cattle or deer, and fire. In sclerophyll forests, 223 endemic phanerogam species occur and 59 of these are specific to this forest type. Several of the 59 specific species are known only from a few plants at a single locality and are critically endangered. Pittosporum tanianum sp. nov. became extinct shortly after its discovery in 1988, and becomes the first documented plant extinction in New Caledonia. A further 15 species of New Caledonian plants, not recorded for several decades, are discussed, and it is concluded that between 4 and 9 of them may be extinct. The existing reserves containing sclerophyll forests are inadequate to protect the remaining biodiversity of the forests. Four immediate steps needed to protect sclerophyll forests are (i) restoration of Leprédour Island; (ii) purchase and restoration of selected privately owned forests; (iii) management of publicly owned forest near Népoui; and (iv) ex situ conservation of certain species.

Conservation Priorities in a Biodiversity Hotspot: Analysis of Narrow Endemic Plant Species in New Caledonia

New Caledonia is a global biodiversity hotspot facing extreme environmental degradation. Given the urgent need for conservation prioritisation, we have made a first-pass quantitative assessment of the distribution of Narrow Endemic Species (NES) in the flora to identify species and sites that are potentially important for conservation action. We assessed the distributional status of all angiosperm and gymnosperm species using data from taxonomic descriptions and herbarium samples. We characterised species as being NES if they occurred in 3 or fewer locations. In total, 635 of the 2930 assessed species were classed as NES, of which only 150 have been subjected to the IUCN conservation assessment. As the distributional patterns of un-assessed species from one or two locations correspond well with assessed species which have been classified as Critically Endangered or Endangered respectively, we suggest that our distributional data can be used to prioritise species for IUCN assessment. We also used the distributional data to produce a map of “Hotspots of Plant Narrow Endemism” (HPNE). Combined, we used these data to evaluate the coincidence of NES with mining activities (a major source of threat on New Caledonia) and also areas of conservation protection. This is to identify species and locations in most urgent need of further conservation assessment and subsequent action. Finally, we grouped the NES based on the environments they occurred in and modelled the habitat distribution of these groups with a Maximum Entropy Species Distribution Model (MaxEnt). The NES were separable into three different groups based primarily on geological differences. The distribution of the habitat types for each group coincide partially with the HPNE described above and also indicates some areas which have high habitat suitability but few recorded NES. Some of these areas may represent under-sampled hotspots of narrow endemism and are priorities for further field work.

The metal hyperaccumulators from New Caledonia can broaden our understanding of nickel accumulation in plants

While an excess of metals such as zinc, cadmium or nickel (Ni) is toxic for most plants, about 500 plant species called hyperaccumulators are able to accumulate high amounts of these metals. These plants and the underlying mechanisms are receiving an increasing interest because of their potential use in sustainable biotechnologies such as biofortification, phytoremediation, and phytomining. Among hyperaccumulators, about 400 species scattered in 40 families accumulate Ni. Despite this wide diversity, our current knowledge of the mechanisms involved in Ni accumulation is still limited and mostly restricted to temperate herbaceous Brassicaceae. New Caledonia is an archipelago of the tropical southwest pacific with a third of its surface (5500 km2) covered by Ni-rich soils originating from ultramafic rocks. The rich New Caledonia flora contains 2145 species adapted to these soils, among which 65 are Ni hyperaccumulators, including lianas, shrubs or trees, mostly belonging to the orders Celastrales, Oxalidales, Malpighiales, and Gentianales. We present here our current knowledge on Ni hyperaccumulators from New Caledonia and the latest molecular studies developed to better understand the mechanisms of Ni accumulation in these plants.

Evolutionary relationships of the New Caledonian heterotrophic conifer, Parasitaxus usta (Podocarpaceae), inferred from chloroplast trnL-F intron/spacer and nuclear rDNA ITS2 sequences

Abstract. The phylogenetic position of Parasitaxus (Podocarpaceae) has been inferred from a cladistic analysis of molecular characters from chloroplast and nuclear genomes including all genera of Podocarpaceae. In all 24 most parsimonious trees, based on combined datasets, Phyllocladus resided outside Podocarpaceae s. str. while Lepidothamnus was basal to the latter. Most other genera were arranged in two major clades. The evidence confirms previous studies, which have suggested a relationship between Lagarostrobos, Manoao and Parasitaxus. Parasitaxus is not directly related to its host Falcatifolium taxoides. Instead it appears to be most closely related to Manoao and Lagarostrobos. No other members of this group now occur on New Caledonia. However, if the evolution of Parasitaxus were autochthonous, a free-living member of this group must once have occurred there. An accelerated evolutionary rate of the chloroplast sequence analysed was suggested, indicating that the plant behaves like a holoparasite.

Distribution of Gymnostoma spp. microsymbiotic Frankia strains in New Caledonia is related to soil type and to host-plant species

The diversity of the Frankia strains that are naturally in symbiosis with plants belonging to the Gymnostoma genus in New Caledonia was investigated. A direct molecular characterization of DNA extracted from nodules was performed, followed by characterization by restriction fragment length polymorphism (RFLP) of the ribosomal rrs–rrl (16S–23S) intergenic spacer (IGS) polymerase chain reaction (PCR)‐amplified region. Seventeen different patterns were identified among the 358 microsymbiotic strains studied in the eight species of host plant present in New Caledonia. This genotypical approach permitted us to show that a large diversity existed among the patterns and that these did not exhibit a strict specificity to any host‐plant species comparable with that previously found in the Casuarina and Allocasuarina symbioses in Australia. Despite this lack of specificity, a correspondence analysis nevertheless showed that the distribution of these patterns was related to soil type and to host‐plant species. Furthermore, several Frankia strains were exclusively associated with the ultramafic soils.