Fire modifies the phylogenetic structure of soil bacterial co‐occurrence networks

Fire alters ecosystems by changing the composition and community structure of soil microbes. The phylogenetic structure of a community provides clues about its main assembling mechanisms. While environmental filtering tends to reduce the community phylogenetic diversity by selecting for functionally (and hence phylogenetically) similar species, processes like competitive exclusion by limiting similarity tend to increase it by preventing the coexistence of functionally (and phylogenetically) similar species. We used co‐occurrence networks to detect co‐presence (bacteria that co‐occur) or exclusion (bacteria that do not co‐occur) links indicative of the ecological interactions structuring the community. We propose that inspecting the phylogenetic structure of co‐presence or exclusion links allows to detect the main processes simultaneously assembling the community. We monitored a soil bacterial community after an experimental fire and found that fire altered its composition, richness and phylogenetic diversity. Both co‐presence and exclusion links were more phylogenetically related than expected by chance. We interpret such a phylogenetic clustering in co‐presence links as a result of environmental filtering, while that in exclusion links reflects competitive exclusion by limiting similarity. This suggests that environmental filtering and limiting similarity operate simultaneously to assemble soil bacterial communities, widening the traditional view that only environmental filtering structures bacterial communities.Financial support was provided by the Spanish Ministry of Science and Innovation (R + D Project CGL2011‐29585‐C02‐01), Ministry of Economy and Competitiveness (CGL2014‐58333‐P) and the EU Marie Curie Programme (FP7‐PEOPLE‐2009‐RG‐248155). Experimental burning was organised within the GRACCIE research net (CONSOLIDER‐Ingenio program, Ministry of Science and Innovation, Spain). EPV acknowledges support by the FPI Programme (BES‐2012‐062331) and the ‘Estancias Breves’ Programme (EEBB‐I‐14‐08275) of the Spanish Ministry of Economy and Competitiveness, and MG by the JAE‐Doc Programme (Consejo Superior de Investigaciones Científicas and European Social Fund) and the Ramón y Cajal Programme (Spanish Ministry of Economy and Competitiveness). Valuable comments by several anonymous reviewers are gratefully acknowledged. Authors have no conflict of interest to declare.Peer reviewe