Soil sampling and mesofauna extraction
Fifty-two sites were sampled across the main habitats of the island of Tenerife (Canary Islands), including 16 sites on laurel forest, 12 on thermophilous woodland, 12 on pine forest, and 12 on dry scrubland (Fig. 1B). Distances between sites ranged from a few meters to a maximum of 75 km (Fig. 1B, Table S1). Each site was sampled for: (i) the superficial soil layer (SUP) by removing one square metre of leaf litter and humus, and; (ii) the corresponding deep soil layer (DEEP), collected by extracting 20 litres of soil to a depth of approximately 25-30 cm below where the superficial layer was collected. SUP and DEEP soil samples were processed following the flotation–Berlese–flotation protocol (FBF) of Arribas et al . (2016). Briefly, the FBF protocol is based on the flotation of soil in water, which allows the extraction of the organic (floating) matter containing the soil mesofauna from soil samples. Subsequently, the organic portion is placed in a modified Berlese apparatus to capture specimens alive and preserve them in absolute ethanol. The last part of the FBF protocol includes additional flotation and filtering steps of the ethanol-preserved arthropods using 1-mm and 0.45-µm wire mesh sieves to yield macrofaunal (retained in the 1-mm mesh) and mesofaunal fractions (retained in the 0.45-µm mesh). Additional manual sorting was performed to pool together Coleoptera specimens from both fractions. The remaining macrofauna was stored and not used for this study. This procedure generates two ’clean’ bulk specimen subsamples for each soil layer, one including all adult and larval Coleoptera (beeltles) and a second with the smallest mesofauna typically dominated by Acari (mites) and Collembola (springtails).