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).