Environmental DNA extraction from soil samples
Microbial DNA was extracted from 0.5 g of soil from each of the 100 samples using the Power Soil DNA isolation kit (MO BIO Laboratories, Carlsbad, CA, USA) according to the manufacturer’s instructions, as it has been shown to be a robust method for DNA extraction from soils (Mahmoudi et al. 2011). The DNA samples were grouped into consortia composed of 5 DNA extractions, which kept altitudinal similarity (supplementary Table 2). The quality and size of the DNA were verified by electrophoresis in 1% agarose gel. Quality control of the extracted DNA was performed to measure (A260/A280and A260/A230 ratios). The DNA concentration was determined using Qubit Fluorometric Quantitation (Life Technologies, Carlsbad, CA, USA). To verify the size of PCR enriched fragments, the template size distribution was checked by running on an Agilent Technologies 2100 Bioanalyzer using a DNA 1000 chip.