Could landscape ecology principles apply at the microscale? A metabarcoding approach on Trichoptera larvae-associated microbial diversity.

Landscape heterogeneity is known as a major factor of community structure and composition. Whether this effect of the landscape extends at different scales and particularly at the relevant scale for microorganisms remained to be determined. We used the cases produced by aquatic larvae of Trichoptera, which assemble organic or mineral particles, as naturally replicated experimental systems representing structured substrates to determine the effect of landscape structuration on microbial communities. A metabarcoding approach was used to characterise fungal, bacterial and diatom communities on cases produced by six Trichoptera species and related unstructured organic and mineral substrates. The structuration of the particles constituting the cases was also determined as a measure of microscale landscape. Structured substrates harboured communities of diatoms, fungi and bacteria that differed from those found on unstructured substrates. Microbial communities also differed between organic and mineral substrates. We found a higher microbial diversity on structured substrates than on unstructured substrates. The heterogeneity of the microscale landscape also affected bacterial and fungal communities within cases. These results highlight the importance of microscale landscape structuration for microbial diversity and demonstrate that approaches of landscape ecology could be downscaled to the microscale.