title: Environmental and Geographical Factors Structure Soil Microbial Diversity in New Caledonian Ultramafic Substrates: A Metagenomic Approach.
abstract: Soil microorganisms play key roles in ecosystem functioning and are known to be influenced by biotic and abiotic factors, such as plant cover or edaphic parameters. New Caledonia, a biodiversity hotspot located in the southwest Pacific, is one-third covered by ultramafic substrates. These types of soils are notably characterised by low nutrient content and high heavy metal concentrations. Ultramafic outcrops harbour diverse vegetation types and remarkable plant diversity. In this study, we aimed to assess soil bacterial and fungal diversity in New Caledonian ultramafic substrates and to determine whether floristic composition, edaphic parameters and geographical factors affect this microbial diversity. Therefore, four plant formation types at two distinct sites were studied. These formations represent different stages in a potential chronosequence. Soil cores, according to a given sampling procedure, were collected to assess microbial diversity using a metagenomic approach, and to characterise the physico-chemical parameters. A botanical inventory was also performed. Our results indicated that microbial richness, composition and abundance were linked to the plant cover type and the dominant plant species. Furthermore, a large proportion of Ascomycota phylum (fungi), mostly in non-rainforest formations, and Planctomycetes phylum (bacteria) in all formations were observed. Interestingly, such patterns could be indicators of past disturbances that occurred on different time scales. Furthermore, the bacteria and fungi were influenced by diverse edaphic parameters as well as by the interplay between these two soil communities. Another striking finding was the existence of a site effect. Differences in microbial communities between geographical locations may be explained by dispersal limitation in the context of the biogeographical island theory. In conclusion, each plant formation at each site possesses is own microbial community resulting from multiple interactions between abiotic and biotic factors.
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.
authors.forename: Véronique
authors.initials: V
authors.lastname: Gourmelon
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.|CIRAD, UMR AGAP, Nouméa, New Caledonia.
authors.forename: Laurent
authors.initials: L
authors.lastname: Maggia
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Powell
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gigante
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.
authors.forename: Sara
authors.initials: S
authors.lastname: Hortal
authors.affiliation: Société Le Nickel (SLN) - Groupe ERAMET, Département Environnement, Nouméa, New Caledonia.
authors.forename: Claire
authors.initials: C
authors.lastname: Gueunier
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.
authors.forename: Kelly
authors.initials: K
authors.lastname: Letellier
authors.affiliation: Institut Agronomique néo-Calédonien (IAC), Axe 2 "Diversités biologique et fonctionnelle des écosystèmes terrestres", Nouméa, New Caledonia.
authors.forename: Fabian
authors.initials: F
authors.lastname: Carriconde
mesh_terms: D001419:Bacteria / Q000235:genetics; D017753:Ecosystem; D005658:Fungi / Q000235:genetics; D014644:Genetic Variation; D056186:Metagenomics; D009510:New Caledonia; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012988:Soil Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S