Microbial communities interplay with their environment through their functional traits that can be as a response or an effect to the environment. Here we explore how a functional trait – the decomposition of organic matter, can be addressed based on genetic markers and how the expression of these markers reflect ecological strategies of two fungal litter decomposer Gymnopus androsaceus and Chalara longipes. We sequenced the genomes of these two fungi, as well as their transcriptomes at different steps of Pinus sylvestris needles decomposition in microcosms. Our results highlighted that if the gene content of the two species could indicate similar potential decomposition abilities, the expression levels of specific gene families belonging to the glycoside hydrolase (GH) category reflected contrasting ecological strategies. Actually C. longipes, the weaker decomposer in this experiment, turned-out to have a high content of genes involved in cell wall polysaccharides decomposition but low expression levels, reflecting a versatile ecology compare to the more competitive G. androsaceus with high expression levels of keystone functional genes. Thus we established that sequential expression of genes coding for different components of the decomposer machinery indicated adaptation to chemical changes in the substrate as decomposition progressed. This article is protected by copyright. All rights reserved.