Accessing the subterranean ant fauna (Hymenoptera: Formicidae) in native and modified subtropical landscapes in the Neotropics

Abstract

Several studies have characterized and delimited subterranean ant assemblages. Soil extraction, one of the methods employed to access this fauna, employs the removal of monoliths. One of the most widely used methods for the extraction of soil sampling is called TSBF (developed by the Tropical Soil Biology and Fertility Programme). This method provides relevant data about the species associated with the soil. In the present study we characterized assemblages of subterranean ants using the TSBF method in different subtropical areas of the Neotropics. We considered two sampling designs in different localities. The first design resulted in 315 TSBF samples obtained from layers at distinct depths. The second design resulted in 270 TSBF samples and 270 epigaeic pitfall trap samples. This material was used to delimit the species that occur exclusively in the subterranean stratum (TSBF) and that are not found on the soil surface. A total of 281 species were recorded. Of these, 57 can be considered subterranean, based on their occurrence in subterranean strata. We also verified that the highest occurrence of ants was in the first 10 cm of soil depth. Due to the importance of using methods that efficiently extract the subterranean ant fauna in studies, we suggest the TSBF method should be used to sample ants or to associate this method with epigaeic pitfall traps to delimit strictly subterranean assemblages in specific community stratification studies.

Distribution of epigeic and hypogeic ants (Hymenoptera: Formicidae) in ombrophilous forests in the Brazilian Amazon

“…Due to the particularities of each stratum, differences in ant richness were expected. Previous studies in an Ombrophilous Forest near Manaus (Vasconcelos & Delabie, 2000), in the Ecuadorian Amazon (Wilkie et al, 2010) and in Southern Region of Brazil (Martins et al, 2020) found higher number of ant species on the soil surface. However, this pattern is not always present.…”

“…However, these factors may have different effects depending on the guild or microhabitat studied (Austin, 1985). Several papers have already indicated strong differences between epigeic and hypogeic ant fauna (Fowler et al, 2000;Andersen and Brault, 2010;Ryder Wilkie et al, 2007;Martins et al, 2020), which could lead to different responses even when subjected to similar environmental gradients (Wilkie et al, 2010). However, most of the information on the effect of environmental gradients comes from grounddwelling ants (e.g.…”

A new subterranean species and an updated checklist of Strumigenys (Hymenoptera, Formicidae) from Macao SAR, China, with a key to species of the Greater Bay Area

“…For instance, Strumigenys louisianae Roger, 1863, Strumigenys nr. epinotalis Weber, 1934 and Strumigenys denticulata Mayr, 1887 were retrieved using soil monoliths at a depth of 0–10cm ( Martins et al 2020 ), while the holotype worker of Strumigenys fuarda Bolton, 2000 was collected within a soil core ( Bolton 2000 ). However, soil sampling, if done without removing the upper soil layer, does not preclude the collection of leaf litter ants foraging on the upper surface of a core or monolith.…”

“…This is potentially the case for S. louisianae or S. nr. epinotalis ( Martins et al 2020 ), and as such further observations are required to establish if they are hypo- or epigaeic.…”

“…However, these sampling methods may limit the discovery of some Strumigenys species, especially those with subterranean habits. The extraction of soil monoliths and the use of subterranean traps are effective methods to sample the poorly known subterranean ant fauna ( Andersen and Brault 2010 ; Wong and Guénard 2017 ; Martins et al 2020 ). An increase in their systematic use is likely to uncover new species, including within the genus Strumigenys .…”