2.1. Study area and bulk sampling
The study area comprises Abies religiosa forests which grow at
around 2800-3500 m.a.s.l. in the Nevado de Toluca volcano, which acts as
sky-island in the TMBV
(Mastretta-Yanes et
al., 2015; Rzendowski, 2006). We sampled arthropods from 14 sampling
points distributed in four sites: Tlacotepec (TLC; 3 sampling points),
San Juan de las Huertas (SJH; 3 sampling points), San Bartolo (ASB; 5
sampling points) and Agua Bendita (AAB; 3 sampling points; Figure 1c),
all within the conservation zone of Nevado de Toluca’s natural protected
area (Figure 1a). Sampling was performed during the rainy season of 2015
during mid August and September for all the sites. At each of the 14
sampling points, three sampling blocks of 20 x 15 m were established,
resulting in a total of 42 community samples (Figure 1b). Each sample
consisted in all the specimens collected by 20 pitfall traps distributed
equidistantly inside each sampling, which were left in the field for 15
days, totalling 840 pitfall traps. Sampling blocks were separated by at
least 50 m within each sampling point, and maximum distance among
sampling points was 19 km (Figure 1b). Pitfall traps consisted in a
plastic cup of 13 cm height and 10 cm diameter, with rectangular
perforations of 2 x 1.5 cm length and width, respectively, 8 cm above
the cup base. Lids of the pitfall traps were painted with brown color.
Each perforation was 2 cm apart from one another and 10 cm above the
plastic cup base. Traps were filled with a mixture of 185 ml of ethanol
70% and 15 ml of glycerin (Figure 1b; Figure S1a). Pitfall traps of
each block site (20 traps) were collected after 15 days and pooled in a
single bulk-sample in a bottle containing ethanol at 96%. Sampling was
performed with SEMARNAT permit No. SGPA/DGVS/02641/15.