Soil sampling and sample processing
During 2019, from mid-April to mid-June, we collected soil samples from
44 sites representing the main five forest habitat types of the Troodos
mountain range (described above, Figure 1; Table S1). Our sampling
scheme covered the full extent of the distribution and altitudinal range
that the five tree species exhibit on Troodos, spanning over 65 km along
an east-west axis and 1500 m of elevation range (Figure 1; Table S1). We
collected two soil samples per sampling site corresponding to the
superficial (1 m2 of leaf litter and humus, 5 cm
depth) and the deep layer (30 cm diameter, 30 cm depth, comprising
~20 liters of soil) as described in Arribas et al.
(2021b). The 88 soil samples were subsequently processed using a
standardized flotation-Berlese-flotation protocol to extract the soil
mesofauna as detailed in Arribas et al. (2016, 2021b). This protocol
allows the retrieval of two subsamples of bulk arthropod specimens,
divided according to their body size (typically Acari and Collembola vs. Coleoptera) which are suited for ‘clean’ extraction of whole
organism community DNA. During bulk-sample processing, we additionally
selected ‘voucher’ specimens of Acari, Collembola and Coleoptera
representing broadly the morphological variation observed in these
groups across samples. A total of 176 bulk subsamples and 344 ‘voucher’
specimens were preserved at -20°C in ethanol 100% for molecular
analyses.