Microbial communities assemble into reproducible compositions at high levels of taxonomic and metabolic organization despite adopting alternative states at the species level (Vila et al 2020, Estrela et al 2020). We have been studying the processes underlying this reproducibility across environments by combining genome scale-metabolic models, metabolomics and phylogenetic methods. By leveraging the evolutionary conservation of quantitative metabolic traits we hope to predict the assembly of complex communities across different environments(Vila et al 2023). As part of this work we have also been studying the effects of environmental complexity on community assembly (Estrela et al 2021).