Biogeography of microbial communities in high‐latitude ecosystems: Contrasting drivers for methanogens, methanotrophs and global prokaryotes

Methane‐cycling is becoming more important in high‐latitude ecosystems as global warming makes permafrost organic carbon increasingly available. We explored 387 samples from three high‐latitudes regions (Siberia, Alaska and Patagonia) focusing on mineral/organic soils (wetlands, peatlands, forest), lake/pond sediment and water. Physicochemical, climatic and geographic variables were integrated with 16S rDNA amplicon sequences to determine the structure of the overall microbial communities and of specific methanogenic and methanotrophic guilds. Physicochemistry (especially pH) explained the largest proportion of variation in guild composition, confirming species sorting (i.e., environmental filtering) as a key mechanism in microbial assembly. Geographic distance impacted more strongly beta diversity for (i) methanogens and methanotrophs than the overall prokaryotes and, (ii) the sediment habitat, suggesting that dispersal limitation contributed to shape the communities of methane‐cycling microorganisms. Bioindicator taxa characterising different ecological niches (i.e., specific combinations of geographic, climatic and physicochemical variables) were identified, highlighting the importance of Methanoregula as generalist methanogens. Methylocystis and Methylocapsa were key methanotrophs in low pH niches while Methylobacter and Methylomonadaceae in neutral environments. This work gives insight into the present and projected distribution of methane‐cycling microbes at high latitudes under climate change predictions, which is crucial for constraining their impact on greenhouse gas budgets. Methane cycle is crucial in high‐latitude ecosystems as global warming makes permafrost organic carbon increasingly available. An extensive dataset of methane‐linked microbial communities, physicochemical, climatic and geographic variables was investigated under a standardized methodology. Physicochemistry explained the largest proportion of variation in microbial composition, while geographic distance impacted more strongly methanogens and methanotrophs than the overall prokaryotes. Bioindicators of specific ecological niches were identified. This work gives insight into present and projected distribution of methane‐cycling microbes at high latitudes under climate and environmental change predictions, which is critical to better constrain their impact on GHG budgets.