New Caledonia Research Articles

Abstract 4638: Fine mapping of two GWAS at 9q22 and 14q13 associated with differentiated thyroid cancer risk

Abstract Context: Incidence of differentiated thyroid carcinoma (DTC) varies considerably between countries and ethnic groups. High incidence rates have been reported in Pacific islands, especially in Melanesian women of New Caledonia (NC). DTC was reported as the only cancer for which the contribution of inherited genetic factors exceeds that of environmental factors. Recent genome-wide associations studies (GWAS) have identified several susceptibility loci, the most robust associations were reported for SNPs in chromosomes 9q22 (rs965513 and rs186727) and 14q13 (rs942289 and rs116909734). It remains unclear whether these 4 SNPs represent independent signals of association or if there are other independent signals within each locus. We aimed to replicate the 4 previously identified SNPs at 9q22 and 14q13 in a population of European descent and in the high risk population of Melanesians in NC. We also sought to determine if there are other SNPs with stronger association and if multiple SNPs are independently associated to DTC within each locus. Methods: We included subjects from 2 case-control studies, conducted in Metropolitan France and in New Caledonia. We genotyped and imputed 81 SNPs at 9q22 and 561 SNPs at 14q13 in 625 cases and 776 controls of European ancestry and 244 cases and 189 controls of Melanesian ethnicity. We performed logistic regression using the log-additive model and we conducted conditional analysis to identify independent markers of DTC. Results: At locus 9q22, among Europeans, we replicated the association of DTC with rs965513 (OR = 1.52, p = 5.9 × 10-6) and rs1867277 (OR = 1.38, p = 2.5 × 10-4). No other SNP was significantly associated with DTC after conditioning on rs965513. In Melanesians, ORs for rs965513 and rs1867277 were similar to those observed in Europeans, but no variant was significantly associated with DTC. At locus 14q13, we replicated the SNPs rs944289 (OR = 0.41, p = 4.7 × 10-4) and rs116909374 (OR = 1.97, p = 3.3 × 10-3) in Europeans, and conditional analysis revealed a third independent signal at rs999460. In Melanesians, we replicated the association with rs944289 (OR = 0.74, p = 1.1 × 10-3) but not with rs11699374. The most significant signal was observed for an independent SNP rs1755774 (OR = 0.57, p = 1.6 × 10-5). This variant was also associated with DTC in Europeans (OR = 0.70, p = 7.3 × 10-3). Interestingly, this variant is located in a region containing an uncharacterized lincRNA, which is abundantly expressed in thyroid tissue. Examination of the observed associations of DTC with SNPs cannot account for the striking difference in incidence rates between Europeans and Melanesians. Conclusion: We confirmed the previously reported associations of DTC with SNPs at locus 9q22 and 14q13. No additional other signal was observed at locus 9q22. At locus 14q13, we identified new interesting susceptibility SNPs in both ethnic groups. SNPs at 9q22 and 14q13 cannot explain the very high incidence of DTC in Melanesians compared to Europeans. Citation Format: catherine TCHEANDJIEU, Fabienne LESUEUR, Marie Sanchez, Therese TRUONG, Pascal GUENEL. Fine mapping of two GWAS at 9q22 and 14q13 associated with differentiated thyroid cancer risk. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4638. doi:10.1158/1538-7445.AM2015-4638

Contested sites, land claims and economic development in Poum, New Caledonia

Property relations are often ambiguous in postcolonial settings. Property is only considered as such if socially legitimate institutions sanction it. In indigenous communities, access to natural resources is frequently subject to conflict and negotiation in a ‘social arena’. Settler arrivals and new economic possibilities challenge these norms and extend the arena. The article analyses conflicts and negotiations in the French overseas territory of New Caledonia in the light of its unique settler history and economic activity, focussing on the little-studied remote northern district of Poum on the Caledonian main island Grande Terre. In this region, the descendants of British fishermen intermarried with the majority Kanak clans. We illustrate the interaction between customary conflicts, European settlement, struggles for independence and a desire for economic development. Customary claims are in tension with the attractions of economic growth and service delivery, which has been slow in coming to Poum for reasons largely outside the control of local people.

Filariasis serosurvey, New Caledonia, South Pacific, 2013.

BackgroundLymphatic filariasis (LF) is a major public health problem in the Pacific. As the global prevalence of infection was not known in New Caledonia (NC), a serosurvey study was conducted by determining the prevalence of circulating filarial antigens, as recommended by the World Health Organization.FindingsA cross sectional study on a 2 degree stratified sample was carried out from June to November 2013. Inclusion criteria were: individuals aged 2 to 80 y/o, who had been hospitalized or sought medical care for a non-infectious cause and who had been living in NC for more than 6 months. LF antigenic detection was performed using the immunocromatographic BinaxNOW filariasis card test (ICT).Among the 1,035 individuals tested, 7 were antigenic. The overall LF antigenic prevalence was 0.62% (CI 95% [0.60-0.63]).All patients were unrelated to each other; none of them presented clinical symptoms of LF.Four of the 7 ICT positive patients reported having travelled to LF endemic areas, 2 patients had never traveled outside NC and the last one had only traveled in non-endemic areas.For the 7 ICT positive patients, the research of microfilariae in blood smears and filarial DNA by PCR was negative.ConclusionThe prevalence of filarial antigenemia in NC is less than 1%, the threshold that defines the filarial endemic areas for WHO. Nevertheless, as two patients who had never travelled outside NC and one who had only travelled to non-endemic areas were antigenic, we cannot conclude that NC is totally free of LF.

Fieldwork in a context of decolonization: the example of a French overseas territory (New Caledonia)

Summary: New Caledonia, a French overseas territory in the South Pacific that possesses more than 25% of the world’s nickel reserves, is currently undergoing a process of decolonization, after a period of Civil War in the 1980s. Balanced between demands for independence of the indigenous Kanak population and political affiliation to France, there is a spatial as well as a socio-economic and cultural division of the population. I argue for socially responsible research strategies in a cross-cultural and politically charged context, and outline some of the factors that influenced my own ethnographic work. The researcher’s family background and education affect the structure of relationships and behaviours. Self-presentation and institutional affiliation play an important role in daily fieldwork. Information and data collection as well as publication of research results have to respect intellectual property rights, which are tangible and intangible. An outsider position in a foreign culture can lead to discomfort, which can be tackled by working closely with local researchers and institutions. Research can be useful in this situation, if the results are made available to local people, political actors, and business. Zusammenfassung: Neukaledonien, ein franzosisches Uberseegebiet im Sudpazifik, das uber 25% der weltweiten Nickel reserven besitzt, durchlauft nach dem Burgerkrieg in den 1980er Jahren aktuell einen Entkolonialisierungsprozess. Hinund hergerissen zwischen Unabhangigkeitsforderungen der indigenen Kanaks und politischer Zugehorigkeit zu Frankreich zeigt sich die zweigespaltene Gesellschaft auch in der raumlichen Segregation der Bevolkerung. Dieser postkoloniale Kontext stellt den Forscher/die Forscherin vor besondere Herausforderungen. Neben dem sozio-wirtschaftlichen und politischen Kontext analysiert der vorliegende Artikel unterschiedliche Faktoren, die den Forscher/die Forscherin in seiner ethnographischen Feldforschung beeinflussen. Familiarer Hintergrund und Erziehung der Forscherin/des Forschers haben Auswirkungen auf den Beziehungsaufbau und das Verhalten zu anderen. Die eigene Prasentation und die institutionelle Zugehorigkeit spielen bei der taglichen Arbeit im Feld eine bedeutende Rolle. Bei der Informationsbeschaffung und der Publikation von Forschungsergebnissen ist das Recht auf geistiges Eigentum zu berucksichtigen, welches sowohl materielle wie auch immaterielle Dinge umfasst. Die Outsider-Situation des Forschers in einer fremden Kultur kann zu Unbehagen fuhren, welches durch Zusammenarbeit mit lokalen Forschern oder mit lokalen Institutionen durchbrochen werden kann. Forschung kann in diesem Sinne nutzlich sein, wenn die Ergebnisse Politik, Wirtschaft und lokaler Bevolkerung zuganglich sind.

Understanding fire patterns and fire drivers for setting a sustainable management policy of the New-Caledonian biodiversity hotspot

New Caledonia (NC) is a biodiversity hotspot sheltering terrestrial ecosystems of high ecological and conservation value including tropical dry forests, rainforests, and maquis. However, uncontrolled bushfires threaten this exceptional biodiversity. A science-based fire management policy could reduce the impact of unwanted fires and help facing climate change. However, to date, data on the location, extent, causal factors and spatial patterns of fires had not been collected. We compiled a 13-year-long (1999–2011) spatially-explicit fire database for NC using MODIS and Landsat data. Using boosted regression trees we disentangled the role of anthropogenic factors, physiography, weather and vegetation on fire activity. We also characterized the location of fires and the vegetation composition at the fire edges, in order to determine which ecosystems were especially vulnerable. Fire size distribution was typically asymmetric with many small fires (<10ha) and very few large fires (>500ha). Ignitions were preferentially located close to villages, cities or roads, at low elevation and linked to high values of fire weather index. Fires were larger at the end of the dry season and during El Niño events. Most fires were bushfires burning in savannas, thickets and maquis, while rainforests were rather ‘avoided’ by fire. However, bushfires generally propagated towards forests of high-conservation value, thus increasing the potential for forest edge erosion. As savanna-forest and maquis-forest mosaics are dominant in the landscape, we discuss the extent to which NC could become a ‘fire trap’ where fire cannot be easily extirpated. Based on our spatially-explicit information on fire activity, we make recommendations for a sustainable forest and fire management policy which would balance the traditional use of fire and the conservation of the most valuable ecosystems. In particular, it may help by reducing the damages of large and destructive bushfires ignited during drought peaks.

Relationships Between Clinico-Epidemiological Patterns of Invasive Meningococcal Infections and Complement Deficiencies in French South Pacific Islands (New Caledonia).

Invasive Meningococcal Disease (IMD) is three fold more common in New Caledonia (NC) than in metropolitan France and many IMD cases (35.7%) are due to Y and W135 serogroups. The purpose of our study was to identify IMD risk factors in NC. A retrospective study of all IMD cases that occurred in NC between 2005 and 2011 was conducted. Socio-environmental, clinical and biological data were collected. A search for immune deficiency was proposed to all cases. IMD presentation and outcome were compared according to meningoccal serogroups and the complement deficiency status (C-deficiency). Sixty-six sporadic IMD cases (29 B serogroup, 20 Y or W135, 6 C, 1 A, 10 unknown) occurred in 64 patients often <24 years-old and of Melanesian origin. Five patients died (7.8%). No socio-environmental risk factors were identified. No asplenia, HIV infection or immunoglobulin deficiencies were found. Two patients had diabetes and 28 of 53 (52.8%) patients had C-deficiency including 20 (71.4%) cases of late complement component deficiency. Patients with C-deficiency were mainly Melanesian (92.8%) originating from the Loyalty Islands (62.1%). They were mostly infected with Y/W135 (42.9%) or B serogroups (32.1%). They often developed later and more severe disease than patients without C-deficiency (need for intensive cares in 60% versus 28.0% of cases, p = 0.01). A high prevalence of C-deficiency in the Melanesian population may explain epidemiological and clinical features of IMD in NC. Our results imply an adaptation of meningococcal vaccine strategies in NC.

Epidemiological and molecular features of dengue virus type-1 in New Caledonia, South Pacific, 2001–2013

BackgroundThe epidemiology of dengue in the South Pacific has been characterized by transmission of a single dominant serotype for 3–5 years, with subsequent replacement by another serotype. From 2001 to 2008 only DENV-1 was reported in the Pacific. In 2008, DENV-4 emerged and quickly displaced DENV-1 in the Pacific, except in New Caledonia (NC) where DENV-1 and DENV-4 co-circulated in 2008–2009. During 2012–2013, another DENV-1 outbreak occurred in NC, the third DENV-1 outbreak in a decade. Given that dengue is a serotype-specific immunizing infection, the recurrent outbreaks of a single serotype within a 10-year period was unexpected.FindingsThis study aimed to inform this phenomenon by examining the phylogenetic characteristics of the DENV-1 viruses in NC and other Pacific islands between 2001 and 2013. As a result, we have demonstrated that NC experienced introductions of viruses from both the Pacific (genotype IV) and South-east Asia (genotype I). Moreover, whereas genotype IV and I were co-circulating at the beginning of 2012, we observed that from the second half of 2012, i.e. during the major DENV-1 outbreak, all analyzed viruses were genotype I suggesting that a genotype switch occurred.ConclusionsRepeated outbreaks of the same dengue serotype, as observed in NC, is uncommon in the Pacific islands. Why the earlier DENV-1 outbreaks did not induce sufficient herd immunity is unclear, and likely multifactorial, but the robust vector control program may have played a role by limiting transmission and thus maintaining a large susceptible pool in the population.

A new genus and species of felt scale (Hemiptera: Coccoidea: Eriococcidae) from New Caledonia.

A new genus of Eriococcidae, Choneochiton Hodgson, is introduced to take a new species, Choneochiton casuarinae Hodgson, Mille & Cazères, off Casuarina collina (Casuarinaceae) from New Caledonia. All stages except the pupa and prepupa are described and illustrated. The new species is thought to be endemic to New Caledonia.

Exploring the Diversity of “Smooth Chanterelles” (Cantharellus, Cantharellales)

Abstract This paper explores the interesting diversity within the group of “smooth chanterelles” and introduces several new taxa from the tropics: C. sublaevis Buyck & Eyssart. and C. cibarioides (Heinem.) Buyck comb. nov. from Africa, C. eccentricus Buyck & V. Hofstetter and C. neocaledonicus Buyck, V. Hofstetter, Eyssart. & Ducousso from New Caledonia and C. incrassatus Buyck & V. Hofstetter from Malaysia.

Impact of &lt;i&gt;Puccinia psidii&lt;/i&gt; on M257;ori taonga plant species

Myrtle rust caused by the pathogen Puccinia psidii sensu lato is a disease of species in the plant family Myrtaceae that is not found in New Zealand It originates in South America but it has steadily spread around the world and is now found in Australia and New Caledonia While the potential economic and environmental impact of myrtle rust establishment in New Zealand has been well documented the potential sociocultural consequences including those for M257;ori have not All New Zealand Myrtaceae species including indigenous species are at risk from P psidii infection but the potential impact on their health is not known All indigenous Myrtaceae species can be considered as Taonga (or treasure) by M257;ori who have utilised the properties (eg spiritual medicinal construction tools food) of some species in many ways both tangible and intangible Optimally preparedness and response plans for a myrtle rust incursion in New Zealand should consider the unique spiritual and other values that M257;ori associate with these plants

Immune response to influenza vaccine and pneumococcal polysaccharide vaccine under IL-6 signal inhibition therapy with tocilizumab

Objectives. To evaluate humoral immune response to influenza vaccine and polysaccharide pneumococcal vaccine in patients with rheumatoid arthritis (RA) or Castleman's disease (CD) during tocilizumab therapy.Methods. Thirty-eight patients (28 RA and 10 CD) receiving tocilizumab and 39 RA patients receiving TNF inhibitors and/or synthetic DMARDs subcutaneously received a single dose of a split-virion inactivated influenza vaccine containing A(New Caledonia (NC):H1N1), A(Hiroshima (HIR):H3N2) and B(Malaysia (MAL)) strains. Twenty-one RA patients using tocilizumab also received 23-valent polysaccharide pneumococcal vaccine. Antibody titers were measured every 4 weeks for a total of 12 weeks after vaccination.Results. In the tocilizumab group, seroprotective titers (40-fold or more) were obtained in 36/38(95%) for A(NC), 35/38(92%) for A(HIR) and 32/38(84%) for B(MAL). In the patients with baseline antibody titer < 40-fold, 11/11(100%), 7/8(88%) and 18/20(90%) patients showed four-fold or more increase in the titer from baseline to A(NC), A(HIR) and B(MAL), respectively. Patients using TNF inhibitors and/or DMARDs showed similar responses. Pneumococcal antibody titers increased at least two-fold in more than 9 of 12 serotypes, which continued for longer than 12 weeks in all the patients.Conclusion. Interleukin-6 (IL-6) blocking therapy with tocilizumab did not affect the humoral immune response to both influenza and pneumococcal vaccines.

A REVIEW OF THE INDO-WEST PACIFIC CONGRID FISHES OF GENERA RHYNCHOCONGER AND BATHYCONGRUS WITH THE DESCRIPTION OF THREE NEW SPECIES

ABSTRACT Two species of the genus Rhynchoconger are recognized from the Indo-West Pacific, namely R. ectenurus (Jordan & Richardson, 1909) and R. trewavasae n.sp. The new species was found in the Gulf of Aqaba (Red Sea) and one specimen was obtained from the Mediterranean coast of Israel. Eight species of the genus Bathycongrus (often referred to as Congrina or Rhechias) are described, among them two new species: B. baranesi found in the Philippines, Japan, and Mozambique; and B. randalli known from the Philippines, South China Sea, and northwestern Australia. B. guttulatus (Gunther, 1887) is a senior synonym of Congermuraena aequorea Gilbert & Kramer, 1897 and of Bathycongrus me galops Fowler, 1934. Its distribution extends from Hawaii, Fiji, New Caledonia, northwestern Australia, and the Philippines to the Gulf of Aden. B. nasicus (Alcock, 1893) designated by Ogilby (1898) as the type of the genus, is known from the Bay of Bengal, Gulf of Aden, and Arabian Sea. B. macrocercus (Alcock, 1894) is known fro...

Risk Factors and Predictors of Severe Leptospirosis in New Caledonia

BackgroundLeptospirosis is a major public health concern in New Caledonia (NC) and in other tropical countries. Severe manifestations of the disease are estimated to occur in 5–15% of all human infections worldwide and factors associated with these forms are poorly understood. Our objectives were to identify risk factors and predictors of severe forms of leptospirosis in adults.Methods and FindingsWe conducted a retrospective case-control study of inpatients with laboratory-confirmed leptospirosis who were admitted to two public hospitals in NC in 2008–2011. Cases were patients with fatal or severe leptospirosis, as determined by clinical criteria. This approach was meant to be pragmatic and to reflect the routine medical management of patients. Controls were defined as patients hospitalized for milder leptospirosis. Risk and prognostic factors were identified by multivariate logistic regression. Among the 176 patients enrolled in the study, 71 had criteria of severity including 10 deaths (Case Fatality Rate = 14.1%). Three risk factors were independently associated with severe leptospirosis: current cigarette smoking (OR = 2.94 [CI 1.45–5.96]); delays >2 days between the onset of symptoms and the initiation of antibiotherapy (OR = 2.78 [CI 1.31–5.91]); and Leptospira interrogans serogroup Icterohaemorrhagiae as the infecting strain (OR = 2.79 [CI 1.26–6.18]). The following post-admission laboratory results correlated with poor prognoses: platelet count ≤50,000/µL (OR = 6.36 [CI 1.79–22.62]), serum creatinine >200 mM (OR = 5.86 [CI 1.61–21.27]), serum lactate >2.5 mM (OR = 5.14 [CI 1.57–16.87]), serum amylase >250 UI/L (OR = 4.66 [CI 1.39–15.69]) and leptospiremia >1000 leptospires/mL (OR = 4.31 [CI 1.17–15.92]).ConclusionsTo assess the risk of developing severe leptospirosis, our study illustrates the benefit for clinicians to have: i) the identification of the infective strain, ii) a critical threshold of qPCR-determined leptospiremia and iii) early laboratory results. In New Caledonia, preventative measures should focus on early presumptive antibacterial therapy and on rodent (reservoir of Icterohaemorrhagiae serogroup) control.

Le référentiel taxonomique Florical et les caractéristiques de la flore vasculaire indigène de la Nouvelle-Calédonie

ABSTRACT The taxonomic reference base Florical and characteristics of the native vascular flora of New Caledonia. The floristic inventory presented here comprises the evolving computerised database Florical (http://www.botanique.nc/herbier/florical). As of the date of publication, it lists all native vascular plant species (as well as infraspecific taxa) present in the territory of New Caledonia, whether validly published or in press, along with their basionym, organised according to the most recent classifications systems (APG III 2009 for the angiosperms, Smith et al. [2006] for the ferns and lycophytes, and Mabberley [2009] for the gymnosperms), accompanied by their status (native or endemic) and the various vegetation types in which they occur. After a brief historical review of our knowledge of New Caledonian botany, the characteristics (richness, composition and endemism) of the different taxonomic groups (ferns and lycophytes, gymnosperms and then angiosperms -mono- and dicotyledons) are analyzed, ...

Chikungunya Virus and the Mosquito Vector Aedes aegypti in New Caledonia (South Pacific Region)

Chikungunya virus (CHIKV) is transmitted to humans through the bite of Aedes mosquitoes. During the 2005-2006 epidemic that occurred in the Indian Ocean Islands, a viral strain harboring a substitution of an alanine to valine at position 226 (E1-A226V) of the E1 glycoprotein enhanced the transmissibility of CHIKV by Aedes albopictus. In March 2011, autochthonous transmission of CHIKV was reported in New Caledonia (NC), an island located in the southwest Pacific Ocean. This was the first report of local chikungunya (CHIK) transmission in this region of the world. Phylogenetic analysis based on the complete genome demonstrated that the CHIKV-NC strain isolated from the first autochthonous human case belongs to the Asian lineage. This is consistent with the Indonesian origin of CHIK cases previously imported and detected. Thus the CHIKV-NC does not present a valine substitution at position E1-226. In New Caledonia, the putative vector of CHIKV is Aedes aegypti, since no other potential vector has ever been described. For example, A. albopictus is not found in NC. Vector competence experiments showed that A. aegypti from New Caledonia was able to transmit, as early as 3 days post-infection, two CHIKV strains: CHIKV-NC belonging to the Asian lineage, and CHIKV-RE from Reunion Island harboring the E1-A226V mutation. Thus the extrinsic incubation period of both CHIKV strains in this vector species could be considered to be quite short. These results illustrate the threat of the spread of CHIKV in the South Pacific region. From February to June 2011 (the end of the alert), only 33 cases were detected. Implementation of drastic vector control measures and the occurrence of the cold season probably helped to limit the extent of the outbreak, but other factors may have also been involved and are discussed.

The genus Bradysia Winnertz (Diptera, Sciaridae) in New Caledonia, with the description of thirteen new species

The following species of the genus Bradysia Winnertz, 1867 are recognized from New Caledonia, all newly described: Bradysia aequispina sp. n., B. centidens sp. n., B. clavistylis sp. n., B. filigera sp. n., B. gemellata sp. n., B. gibbosa sp. n., B. melina sp. n., B. nudilobata sp. n., B. paucidens sp. n., B. planistylata sp. n., B. seticornis sp. n., B. spissa sp. n. and B. stricta sp. n. A key to the species is given.

Birds of Melanesia: Bismarcks, Solomons, Vanuatu, and New Caledonia by Guy Dutson

Birds of Melanesia: Bismarcks, Solomons, Vanuatu, and New Caledonia by Guy Dutson

Myxomycetes from Papua New Guinea and New Caledonia

We present a compilation of all myxomycetes recorded from Papua New Guinea (PNG) and New Caledonia (NC). Specimens were collected during field trips in September 1983–January 1984 to both territories and in August 1991, October 2007, and April 2009 to NC. Bark and dung samples for moist chamber cultures were collected during the field trips in September 1983–January 1984 (PNG and NC) and in August 1991 and October 2007 (NC). In addition, information from previous publications and unpublished specimens in the herbarium at the Plant Protection Instituted in Port Moresby, PNG, are included. A total of 180 species are reported. Of the 63 species from PNG 51 are new to the country, and 123 of the 149 species from NC are new to the territory.

Paradisi australi in bilico tra etero e autorappresentazioni: le isole francesi del Pacifico meridionale

The South Pacific is a region still unimportant in the world scene, where there are islands which are extremely variable in size and are often gathered in archipelagos. Since it was long neglected by the processes of colonialism, the region has managed to preserve a rich environmental and cultural heritage, abundant and unusual in the European hetero-perception. The region was first considered as a far and wild paradise to tame and exploit in the name of geopolitics and the economy, and is now divided into two linguistic areas, English and French. This situation has not prevented the creation of narratives, representations and stereotypes around this idyllic region and its elements of wilderness, mystery, remoteness, exoticism, isolation.This article focuses on the French islands in the South Pacific: New Caledonia, Polynesia and Wallis and Futuna. Beyond their stereotypes and hetero images (tropical paradises, smiling populations), such islands present some extremely varied forms of spatial organization and land management, depending on physical realities, cultural heritage, social, political and economical processes. While traditional tourism promotes the image of tropical paradise, their self-representations are trying to show a different vision, which increases the differences between the three French archipelagos of the South Pacific.

Biodiversity of Mimosa pudica rhizobial symbionts (Cupriavidus taiwanensis, Rhizobium mesoamericanum) in New Caledonia and their adaptation to heavy metal-rich soils

Rhizobia are soil bacteria able to develop a nitrogen-fixing symbiosis with legumes. They are taxonomically spread among the alpha and beta subclasses of the Proteobacteria. Mimosa pudica, a tropical invasive weed, has been found to have an affinity for beta-rhizobia, including species within the Burkholderia and Cupriavidus genera. In this study, we describe the diversity of M. pudica symbionts in the island of New Caledonia, which is characterized by soils with high heavy metal content, especially of Ni. By using a plant-trapping approach on four soils, we isolated 96 strains, the great majority of which belonged to the species Cupriavidus taiwanensis (16S rRNA and recA gene phylogenies). A few Rhizobium strains in the newly described species Rhizobium mesoamericanum were also isolated. The housekeeping and nod gene phylogenies supported the hypothesis of the arrival of the C. taiwanensis and R. mesoamericanum strains together with their host at the time of the introduction of M. pudica in New Caledonia (NC) for its use as a fodder. The C. taiwanensis strains exhibited various tolerances to Ni, Zn and Cr, suggesting their adaptation to the specific environments in NC. Specific metal tolerance marker genes were found in the genomes of these symbionts, and their origin was investigated by phylogenetic analyses.