Unexpected microbial diversity in new Caledonia’s ultramafic ecosystems with conservation implications in a biodiversity hotspot

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Ripoll, Julie | Stenger, Pierre-Louis | Nuñez, Nicolas Fernandez | Demenois, Julien | Stokes, Alexia | Gourmelon, Véronique | Dinh, Kelly | Robert, Nadia | Drouin, Julien | Mournet, Pierre | Léopold, Audrey | Read, Jennifer | Gardes, Monique | Maggia, Laurent | Carriconde, Fabian

Edité par CCSD ; Nature Publishing Group -

Data availability: DNA librairies: the Illumina MiSeq sequences are available under the following NCBI accession numbers: SAMN05786746 to SAMN05786777 for Rivière Blanche and Kopéto; SUB9939738, SUB9957890, SUB9966585, SUB9965709 and SUB9966666 for Goro; SAMN31953029 to SAMN31953058 and SAMN31953148 to SAMN31953177 for Maré; SRR30291378 to SRR30291403 for Bois du Sud and Tiébaghi.. International audience. Soils harbour an incredible diversity of microorganisms that play crucial roles in ecosystem functioning. However, this biodiversity remains largely overlooked, with a poor understanding of how patterns form across landscapes. An eDNA metabarcoding approach was used to identify potential overarching patterns in fungal and bacterial communities from ultramafic ecosystems in New Caledonia, a renowned biodiversity hotspot. Our comprehensive analysis revealed several key findings, notably an important microbial diversity in the extreme environments of iron crust soils. Clear tendencies in phyla composition were also observed, with the fungal groups Ascomycota and Mucoromycota acting as potential indicators of land degradation (only in lateritic soils for Mucoromycota). For bacteria, Chloroflexi was characteristic of open vegetation, while Proteobacteria and Cyanobacteria were observed in higher relative abundances in the closed vegetation. The ectomycorrhizal fungal functional group was also found to be rich and unique, with a hypothetical endemism rate of 87%, and over-represented by the Cortinarius genus in rainforests and maquis (shrublands) dominated by ectomycorrhizal plants. Finally, each ultramafic Massif demonstrated a unique microbial community. Thus, our findings provide valuable insights into microbial ecology and emphasize the need for tailored conservation strategies for this biodiversity hotspot.

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