Based on analysis of sequences with the small subunit of the nuclear ribosomal RNA gene (18S), all DSE are within ascomycetes and include taxa in the orders Pleoporales, Microascales, Xylariales, Pezizales, Dothideales, Leotiales, Chaetothyriales, Elaphomycetales, Eurotiales, Onygenales, Saccharomycetales, Neolectales, Taphrinales, Mitosporic, and nonsporulating cultures.
Studies in alpine and semi-arid ecosystems have shown that dark septate endophytes are more prevalent than arbuscular mycorrhizae in these environments.
[3] They are capable of breaking down many organic compounds including starch, cellulose, laminari, xylan, gelatin, and RNA[4] from detrital nutrient pools.
[2] Dark septate endophytes have been observed across the plant kingdom in Dicotyledoneae and Monocotyledonae (Angiospermae), and Equisetopsida, Lycopsida, Polypodiopsida, and Psilotopsida (Gymnospermae).
[1] Dark septate endophytes frequently co-occur with mycorrhizal fungi such as arbuscular, ericoid, orchid, and ectomycorrhiza.
[1][6] In arid ecosystems, DSE in the order Pleosporales are commonly found in both rhizosphere soils and surface biological soil crust communities, which suggests that they may aid in nutrient absorption by plants by linking plant roots and biological soil crusts that fix carbon and nitrogen in hyphal networks, which forms the basis of the Fungal Loop Hypothesis[7] The melanized cell walls of DSE may affect heat dissipation or form complexes with oxygen radicals in plant hosts, which can alter host thermal tolerance.
Similar to other mycorrhizal fungi, DSE can protect hosts from pathogens or herbivores through the production of inhibitory metabolites, physical exclusion of other microorganisms, or melanized hyphae.