Epigaeic and hypogaeic ant abundance data from 20 sites spanning a 1000 km gradient in Northern Australia

Studies using climatic gradients play a key role in our understanding of the importance of rainfall and temperature as factors regulating species diversity and distribution, and thus of likely responses to climate change. However, such studies currently consider above-ground species only, ignoring the diverse hypogaeic (subterranean) invertebrate fauna. Here, we assess the extent to which the responses of hypogaeic ant assemblages to a rainfall gradient in the Australian seasonal tropics are congruent with those of epigaeic (ground-dwelling) assemblages. We sampled at 20 sites covering a gradient of over 1000 km and 1100 mm in mean annual rainfall (MAR). We predicted that the different assemblages would display contrasting patterns because the epigaeic fauna is highly arid-adapted whereas the hypogaeic fauna is mesic-adapted in Australian savannas. We collected 392 epigaeic and 17 hypogaeic species. Epigaeic ant abundance and species diversity tended to increase with decreasing rainfall..., Study sites
Our study was conducted along an extended North Australian Tropical Transect (NATT) in the Northern Territory, running from the northern coast inland toward central Australia. In September 2023, we sampled 20 equidistant sites over a transect of 1000 km, 383 – 1563 mm MAR (Figure 1, Table S1). All sites supported eucalypt-dominated tropical savanna on well-drained sandy or loamy soils.

Sampling
At each site, we arranged a 2 x 10 grid with 10 m spacing, where each point represents the location of one ground pitfall trap (diameter = 4.2 cm) and two subterranean baited pitfall traps (with 4 side entrance holes with diameter = 2.5 mm) placed at a depth of 10 cm. The baits in subterranean traps consisted of an equal mixture of tuna, peanut butter, and honey, which we spread as an inside coating near the aperture of the traps. We chose this mixture to attract a maximum number of ant species, which would find the baits attractive whether they were foraging for carbohydrates, prote..., # Data from: Epigaeic and hypogaeic ant abundance data from 20 sites spanning a 1000 km gradient in Northern Australia

Dataset DOI: [10.5061/dryad.x3ffbg80s](https://doi.org/10.5061/dryad.x3ffbg80s)

## Description of the data and file structure

This data consists of ant species abundance from pitfall and subterranean traps. We used 400 pitfall traps and 800 subterranean traps across 20 sites, spaced 50 km apart, in Northern Australia. We extracted, identified, and counted ants in each trap.

### Files and variables

#### File: NATT_dryad_code.R

**Description:** R code for abundance analysis

#### File: NATT_ants_dryad.csv

**Description:** 

##### Variables

* site: Site number, ordered from North to South
* location: Name of site locality
* final_lat: latitude for site 
* final_long: longitude for site
* method: ant trapping method used, either pitfall of subterranean trap
* trap_nb: trap number
* trap_id: unique trap identification (combination of trap and site number)
* subfamily..., ,