MIV samples treatment and identification of taxa
In total, 864 samples were collected, fixed with 90% ethanol in the field and then transported to the laboratory. MIV were separated from other organic and inorganic material. The individuals were sorted and identified to family or, in some cases, to lower taxonomic levels (i.e., Oligochaeta, Hydracarina, Lepidoptera) following the identification key of Tachet, Richoux, Bournaud and Usseglio-Polatera (2000) and were then counted (Appendix C in Data S1). Pupae, adult individuals in a non-aquatic life stage and terrestrial invertebrates were excluded.