15 págs.- 6 figuras.- 75 referenciasArchaea represent a diverse group of microorganisms often associated with extreme environments. However, an integrated understanding of biogeographical patterns of the specialist Haloarchaea and the potential generalist ammonia-oxidizing archaea (AOA) across large-scale environmental gradients remains limited. We hypothesize that niche differentiation determines their distinct distributions along environmental gradients. To test the hypothesis, we use a continental-scale research network including 173 dryland sites across northern China. Our results demonstrate that Haloarchaea and AOA dominate topsoil archaeal communities. As hypothesized, Haloarchaea and AOA show strong niche differentiation associated with two ecosystem types mainly found in China's drylands (i.e. deserts vs. grasslands), and they differ in the degree of habitat specialization. The relative abundance and richness of Haloarchaea are higher in deserts due to specialization to relatively high soil salinity and extreme climates, while those of AOA are greater in grassland soils. Our results further indicate a divergence in ecological processes underlying the segregated distributions of Haloarchaea and AOA. Haloarchaea are governed primarily by environmental-based processes while the more generalist AOA are assembled mostly via spatial-based processes. Our findings add to existing knowledge of large-scale biogeography of topsoil archaea, advancing our predictive understanding on changes in topsoil archaeal communities in a drier world.This research was supported by the National Natural Science Foundation of China (Nos. 31700463 and 31770430), National Scientific and Technological Program on Basic Resources Investigation (No. 2019FY102002), Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment, China (No. 2019HJ2096001006), the Top Leading Talents in Gansu Province to J.D. and the Innovation Base Project of Gansu Province (No. 20190323). J.C.S. was supported by the U.S. Department of Energy-BER program, as part of an Early Career Award to J.C.S. at the Pacific Northwest National Laboratory (PNNL), a multiprogram national laboratory operated by Battelle for the US Department of Energy under Contract DEAC05-76RL01830. M.D.-B. acknowledges support from the Spanish Ministry of Science and Innovation for the I +-D + i project PID2020-115813RA-I00 funded by MCIN/AEI/10.13039/501100011033. M.D.-B. is also supported by a project of the Fondo Europeo de Desarrollo Regional (FEDER) and the Consejería de Transformacion Economica, Industria, Conocimiento y Universidades of the Junta de Andalucía (FEDER Andalucía 2014–2020 Objetivo tematico ‘01 - Refuerzo de la investigacion, el desarrollo tecnologico y la innovacion’) associated with the research project P20_00879 (ANDABIOMA).Peer reviewe
