Continental sampling of fungi Targeted Locus (Loci)

We assayed soils from 47 sites in North and South America. The sites represented a wide range in latitude (28 °S to 69 °N), mean annual temperature (–9.3 to 25.0 °C), and mean annual precipitation (150 to 5000 mm y-1). The top 5 cm of mineral soil was composited from 5–10 locations within a given site, near the peak plant growing season. These soil samples (and their ID numbers) were identical to a subset of those reported in Fierer and Jackson (2006). DNA was extracted from 5–10 g dry wt of each soil sample. We used universal fungal primers of Borneman & Hartin (2000) modified for barcoded pyrosequencing to amplify a ~422 bp region of the 18S rRNA gene.