2.2 Field sampling
The field survey consisted of several activities. First, we established the vertical sampling system in April 2002 via a 200 m long application of “canopy trekking” to access the forest trees to secure the horizontal traverse line (Dial et al. 2004a). Once the 130 m traverse line was secured near the top of the three tallest trees, each > 65 m above ground level, we suspended seven vertical transects (Fig. 1). We used these vertical transects to sample the canopy interior systematically from 1 m above ground to the traverse line 55-65 m above ground. Finally, we collected instantaneous measures of photosynthetically active radiation with a handheld meter, temperature and humidity with suspended data logging sensors, and fogging samples in May 2002 (Dial et al. 2006).
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. 1). 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 ground (Fig. 1). 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. In total, we obtained and identified ant assemblage samples for 63 out of 86 sampling points with 14 samples having no ants and 9 samples having been lost between sampling and analysis. 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.