Data on: Modelling selection, drift, dispersal and their interactions in the community assembly of Amazonian soil mites

Data on species abundance, species traits and environmental variables
for 55 sites sampled over a lowland rainforest landscape in central Amazonia,
Brazil.

Files "Oribatida_Ducke_55.csv",
"Traits_Ducke_55.csv", and "Environment_Ducke_55.csv"
provide the raw community, trait and environmental data used in the study,
respectively. File "ESM2_Oeco.doc" provides a short description of
the R script used to analyze the data, and file
"Metacommunity_Rscript_dataS1_Oeco.R" is a commented R script
containing all analyzes performed.

The data were obtained as part of the Brazilian Program for Biodiversity
Research (PPBio) in Reserva Ducke, a large reserve of primary tropical
rainforest (10 x 10 km) in Manaus, Brazil (2°57’S, 59°56’W) (Costa and
Magnusson 2010). The reserve is under administration of the National Institute for
Amazonia Research (INPA). Mite sampling was carried out from March 18 to
May 13, 2002. Mites were collected from 55 sites distributed over a grid in the
reserve, with at least 1 km between them. On each site, one 250-m transect was
established along a topographic contour lines, in order to minimize
environmental variation within it. Then, one soil core (3.5 cm x 3.5 cm x 5 cm)
was sampled each 12.5 m along the transect, with 20 cores per transect and 55
sites × 20 cores = 1100 cores overall. Within-site soil cores thus provided a
representative sample of the local, site-level community, which was the
sampling unit of the study. To reduce the large sample processing load, each
four consecutive soil cores within transects were combined as a compound soil
sample. Compound samples were kept in plastic containers and transported to the
Laboratory of Systematics and Ecology of Terrestrial Arthropods at INPA’s
campus in Manaus, where animals were extracted using a Berlese-Tullgren apparatus.
Samples were gradually heated from 28 to 45 ºC until they were completely dry,
which took from six to seven days. Extracted animals were preserved in glass
vials containing 4% formaldehyde solution. All adult oribatid mites were sorted
to morphospecies and identified whenever possible using taxonomic keys.
Identification proceeded by clarifying specimens with lactic acid, followed by
temporary slide-mounting and examination under a compound microscope. Immatures
were not considered, but represented only 8% of extracted individuals. Voucher
specimens were deposited in the Entomological Collection of INPA.

We estimated the mean body mass of each sampled species by measuring
1–15 individuals of each sampled species, depending on their abundance. For
each individual, body length and width (µm) were measured under a microscope,
and body mass (µg) was predicted using a well-established allometric equation (R² =
0.98; Caruso and Migliorini 2009): mass = -17.17 + 3.0log(length+width). Then,
the mean body mass was calculated for each species. Species reproductive mode
(sexual or parthenogenetic) was inferred using published records. When a
species’ reproductive mode was unknown (i.e. morphospecies with a single
individual), it was inferred from closely related species, if part of a
taxonomic group that is not known to vary in reproductive mode. Otherwise, the
species was assumed to be sexual.

Data were obtained on soil texture (clay content, in %), soil contents
of water (%) and nutrients (C, N and P, in g kg-1) and litter dry
mass (g). Litter dry mass was measured during
mite surveys by marking 50 x 50 cm squares along transects, one each 50 m,
within which all litter was harvested. Litter samples were transported to the
laboratory in plastic containers and dried to constant weight. Further, in each
transect, six soil cores (one each 50 m) were collected to a depth of 5 cm. Soil
cores were pooled in a plastic container and transported to INPA for
granulometric analysis, and to the Brazilian Agricultural Research Corporation
(EMBRAPA), also in Manaus, for nutrient analyses. Soil samples were oven-dried,
cleaned of stones and roots, and passed through a 2 mm sieve. Soil granulometry
was determined using the hydrometer method (clay: <0.002 mm; silt:
0.002–0.05 mm; sand: 0.05–2 mm). As clay and sand contents were highly correlated
(r = -0.99) and silt content was
negligible, we used clay to describe soil texture. Total organic carbon was
measured by wet oxidation, using acid dichromate solution followed by titration
with 0.5N FeSO4 and o-phenalphthroline. Total nitrogen was estimated
using the wet oxidation (Kjeldahl method), by converting organic N to ammonium
(NH4+) for measurement. Available phosphorus was estimated using the ammonium
molybdate–ascorbic acid method, by reading the blue complex formed at 712 nm
under a spectrophotometer. Soil water content was obtained by comparison
between the wet and dry weights of soil samples. Soil and litter measurements were
averaged by site.

References:

Caruso T, Migliorini M (2009) Euclidean geometry
explains why lengths allow precise body mass estimates in terrestrial
invertebrates: the case of oribatid mites. J Theor Biol 256:436–40. doi:
10.1016/j.jtbi.2008.09.033

Costa FRC, Magnusson WE (2010) The need for large-scale,
integrated studies of biodiversity – the experience of the Program for
Biodiversity Research in Brazilian Amazonia. Brazilian J Nat Conserv 8:3–12.