ena-STUDY-UNIVERSITY OF NEUCHATEL-14-11-2018-17:48:22:151-3
Micro-eukaryotic functional diversity associated with Sphagnum mosses in tropical, subtropical and temperate climatic zones
Sphagnum dominated ecosystem play major roles as Carbon sinks at the global level. Associated microbial communities, in particular eukaryotes, play major roles in nutrient fixation and turnover. In order to understand better the ecological processes driven by these organisms, a first step is to characterize these associated organisms.  We characterized the taxonomic diversity and from this inferred the functional diversity of microeukaryotes in Sphagnum mosses in tropical, subtropical and temperate climatic zones through an environmental DNA diversity metabarcoding survey of the V9 region of the small subunit  (SSU) 18S rRNA gene. As microbial processes are strongly driven by temperatures, we hypothesised that saprotrophy would be highest in warm regions, whereas mixotrophy, an optimal strategy in oligotrophic environments, would peak under colder climates. Phylotypes richness was higher in tropical and subtropical climatic zones than in the temperate region, mostly due to a higher diversity of animal parasites (i.e. Apicomplexa). Decomposers, and especially opportunistic yeasts and moulds were more abundant in warmer climates, while mixotrophic organisms were more abundant under temperate climates. The dominance of decomposers, suggesting a higher heterotrophic activity in warmer climate, is coherent with generally observed faster nutrient cycling at lower latitudes. Sphagnum being competitive in low nutrient conditions thrives better under colder climates, thus explaining the lower cover at low latitudes and the negative impact of experimental warming on Sphagnum growth and associated carbon sequestration in peatlands.
Sphagnum dominated ecosystem play major roles as Carbon sinks at the global level. Associated microbial communities, in particular eukaryotes, play major roles in nutrient fixation and turnover. In order to understand better the ecological processes driven by these organisms, a first step is to characterize these associated organisms.  We characterized the taxonomic diversity and from this inferred the functional diversity of microeukaryotes in Sphagnum mosses in tropical, subtropical and temperate climatic zones through an environmental DNA diversity metabarcoding survey of the V9 region of the small subunit  (SSU) 18S rRNA gene. As microbial processes are strongly driven by temperatures, we hypothesised that saprotrophy would be highest in warm regions, whereas mixotrophy, an optimal strategy in oligotrophic environments, would peak under colder climates. Phylotypes richness was higher in tropical and subtropical climatic zones than in the temperate region, mostly due to a higher diversity of animal parasites (i.e. Apicomplexa). Decomposers, and especially opportunistic yeasts and moulds were more abundant in warmer climates, while mixotrophic organisms were more abundant under temperate climates. The dominance of decomposers, suggesting a higher heterotrophic activity in warmer climate, is coherent with generally observed faster nutrient cycling at lower latitudes. Sphagnum being competitive in low nutrient conditions thrives better under colder climates, thus explaining the lower cover at low latitudes and the negative impact of experimental warming on Sphagnum growth and associated carbon sequestration in peatlands.