Figure 2. Study site and design: A) habitat photo of the sampling plot;
B) Map of Sabah with elevation gradient presented (metres above sea
level); C) The top and side view of the transect established within the
forest plot (modified from Dial et al. 2004a and Dial et al. 2006).
Quantifying ant assemblages
Ant assemblages were sampled using insecticide fogging between 0700 and
0930 on 12-24 May 2002 from within the canopy by a climber rappelling
down using a Swing-Fog model SN50 (Phoenix Fogger, Dallas, TX, USA) near
each of seven vertical sample transects. These vertical transects were
suspended from a 130 m horizontal traverse line secured in the upper
canopy and were arranged at 20-25 m intervals horizontally (Fig. 2).
Each of these transects supported multiple individual circular fogging
trays (1 m2) (n=86) suspended in the air with attached
ethanol-filled collecting bottles spaced at approximately 5 m vertical
intervals beginning 1 m above the ground (Fig. 2). These trays collected
knocked-down arthropods that were between trays at the time of fogging.
A 1.6% aqueous solution of the synthetic pyrethrum (Cypermethrin) was
used. Arthropods were collected into 80% ethanol 1-2 hours after
fogging, and ants were separated as part of arthropod ordinal sorting
(see Dial et al. 2006 for results on ordinal arthropod assemblages). The
ants sampled using fogging are mainly diurnal foraging species active
during the sampling period (0700 to 0930), and therefore likely present
a subset of the total local ant diversity.
All worker ants were identified to genus following Fayle et al (2014),
with relevant updates for taxonomy changes (Ward et al. 2015, Borowiec
2016, Ward et al. 2016), and then separated into morphospecies. Where
possible, species names were assigned using online image databases
(www.antweb.org, www.antbase.net), published literature (Hung 1970,
Dorow and Kohout 1995, Schödl 1998, Kohout, 2006a, 2006b) and the
collections of TMF. Reproductive individuals were excluded from the
data, since their presence does not indicate an established colony,
mating flights can confound estimates of abundance, and they can be
challenging to match with workers unless entire nest series are
collected. Lone major workers were also excluded for the latter reason.
While all sample trays were
suspended in the air at systematic, standardized horizontal and vertical
positions, some trays captured no worker ants because there was only
empty space with no foliage or stems between the sample tray without
worker ants and the next sample tray above. In total, we obtained and
identified ant assemblage samples for 61 out of 86 sampling points, with
14 samples having no ants, 9 samples having been lost between sampling
and analysis, 2 samples in Transect 5 (two individuals of ants
discovered) belong to an emergent forest layer with no other horizontal
positions to compare with.