Assessing Biotic and Abiotic Interactions of Microorganisms in Amazonia through Co-Occurrence Networks and DNA Metabarcoding

• Camila Duarte Ritter ^[1] ; Dominik Forster ^[2] ; Josue A. R. Azevedo ^{[3] [6]} ; Alexandre Antonelli ^{[6] [4] [8] [5]} ; R. Henrik Nilsson ^{[6] [4]} ; Martha E. Trujillo ^[7] ; Micah Dunthorn ^{[1] [1]}
  1. [1] University of Duisburg-Essen

     University of Duisburg-Essen

     Kreisfreie Stadt Essen, Alemania

     
  2. [2] University of Kaiserslautern

     University of Kaiserslautern

     Kreisfreie Stadt Kaiserslautern, Alemania

     
  3. [3] Instituto Nacional de Pesquisas da Amazônia

     Instituto Nacional de Pesquisas da Amazônia

     Brasil

     
  4. [4] University of Gothenburg

     University of Gothenburg

     Suecia

     
  5. [5] University of Oxford

     University of Oxford

     Oxford District, Reino Unido

     
  6. [6] Gothenburg Global Biodiversity Centre, Box 461, SE-405 30, Göteborg, Sweden
  7. [7] Departamento de Microbiología y Genética, Campus Miguel de Unamuno, 37007, Salamanca, Spain
  8. [8] Royal Botanic Gardens, Kew, TW9 3AE, Richmond, Surrey, UK

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• Localización: Microbial ecology, ISSN-e 1432-184X, ISSN 0095-3628, Vol. 82, Nº. 3, 2021, págs. 746-760
• Idioma: inglés
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  • Species may co-occur due to responses to similar environmental conditions, biological associations, or simply because of coincident geographical distributions. Disentangling patterns of co-occurrence and potential biotic and abiotic interactions is crucial to understand ecosystem function. Here, we used DNA metabarcoding data from litter and mineral soils collected from a longitudinal transect in Amazonia to explore patterns of co-occurrence. We compared data from different Amazonian habitat types, each with a characteristic biota and environmental conditions. These included non-flooded rainforests (terra-firme), forests seasonally flooded by fertile white waters (várzeas) or by unfertile black waters (igapós), and open areas associated with white sand soil (campinas). We ran co-occurrence network analyses based on null models and Spearman correlation for all samples and for each habitat separately. We found that one third of all operational taxonomic units (OTUs) were bacteria and two thirds were eukaryotes. The resulting networks were nevertheless mostly composed of bacteria, with fewer fungi, protists, and metazoans. Considering the functional traits of the OTUs, there is a combination of metabolism modes including respiration and fermentation for bacteria, and a high frequency of saprotrophic fungi (those that feed on dead organic matter), indicating a high turnover of organic material. The organic carbon and base saturation indices were important in the co-occurrences in Amazonian networks, whereas several other soil properties were important for the co-exclusion. Different habitats had similar network properties with some variation in terms of modularity, probably associated with flooding pulse. We show that Amazonian microorganism communities form highly interconnected co-occurrence and co-exclusion networks, which highlights the importance of complex biotic and abiotic interactions in explaining the outstanding biodiversity of the region.