New records of hunting ants (Poneroids and Ectatomminoids) in the northern part of the Colombian Orinoquia region

New records of hunting ants (Poneroids and Ectatomminoids) in the northern part of the Colombian Orinoquia region.— We reviewed 466 specimens of hunting ant species collected in flooded savanna environments and their adjacent forest fragments in the rural area of Arauca municipality (Arauca, Colombia). Samples were taken from eight forest fragments with sizes between 0.25 and 220 ha. In each location we set linear transects with seven sampling points separated by 20 m. In each sampling point we used three capture methods: a pitfall trap (left 24 hours), a sample of 1 m2 of soil and litter to be processed with a mini Winkler extractor, and direct capture. Fifteen species were recorded; the most diverse genus was Neoponera with six species, followed by Odontomachus with two species and Ectatomma, Anochetus, Gnamptogenys, Prionopelta Pseudoponera, Pachycondyla and Thaumatomyrmex each with one species. This study extends the geographical distribution of 15 hunting ant species to the northern part of the Colombian Orinoquia region and documents for the first time the presence of Thaumatomyrmex cf. mutilatus in Colombia.

New records of hunting ants (Poneroids and Ectatomminoids) in the northern part of the Colombian Orinoquia region J. C. Agudelo Martínez & N. Pérez-Buitrago

Introduction
The Orinoquia region has an area of 251,185 km 2 and represents 22% of the territory of Colombia. It includes the departments of Meta, Casanare, Vichada, Guaviare and Arauca (Hernández-Camacho 1992). This biogeographical region includes ecosystems such as 'altillanuras' (plains), eolic and flooded savannas, with riparian forest, forest remnants and 'morichales' (palm swamps) (Rippstein et al., 2001). These forest habitats are within a savanna matrix, creating a mosaic or reticulated pattern landscape. The biodiversity of the Orinoquia region is presumably similar to the Apure basin in Venezuela. However, the proxi� mity to the Amazonian and Andes regions results in a unique composition of flora and fauna.
The Orinoquia is one of the last wild and virgin landscape regions of the planet (Lasso et al., 2011). However, and possibly due to its "apparent" structural simplicity, studies by the academic and scientific communities on its biodiversity and ecological interactions are scarce in the Orinoquia departments, including Arauca (Arbeláez-Cortéz, 2013). This lack of knowledge may imply a risk for the strategic potential for sustainable development and conservation of the region and its existence in the near future (Agudelo & Pérez-Buitrago, 2015).
Insects play many important ecological roles in tropical savannas, shaping fundamental processes to maintain the structure and function of ecosystems (Andersen et al., 2003). Some ants, for example, may serve as seed dispersers, while others may regulate inver� tebrate populations (Majer, 1983;Alonso, 2000). Also, as a group, ants contribute largely to biomass, abundance and species richness in animal communities in most terrestrial ecosystems (Folgarait, 1998;Underwood & Fisher, 2006). These attributes, along with a well-known and stable taxonomy, high ecological fidelity and easiness of sampling, make ants an optimal taxon for use as ecological indicators both in disturbed and natural environ� ments (Arcila & Lozano-Zambrano, 2003;Andersen & Majer, 2004;Andersen et al., 2004).
Based on their morphology and behavior, hunting ants are considered a primitive group. They are present in all biogeographical regions and occupy several ecological niches. They vary in size, from tiny and cryptic species to large, predator species (Ouelette et al., 2006;Serna & Vergara-Navarro, 2008;Delabie et al., 2015). Bolton (2003) suggested the name 'Poneromorph'' as an informal and non-monophiletic taxon which was previously considered to be in the Ponerinae subfamily (Bolton, 1994). This large taxon includes the families Amblyoponinae, Ectatomminae, Heteroponerinae, Paraponerinae, Ponerinae and Proceratiinae (sensu stricto, Bolton, 2003).
In this study we document the species richness and abundance of hunting ant species in flooded savanna and forest fragments in the municipality of Arauca (Arauca, Colombia). We considered a gradient that included three environments: forest, edge, and flooded savanna matrix. This gradient could contribute to the understanding of the geographical distribution of hunting ants and their natural history in the northern Orinoquia of Colombia.

Study site
Samplings were carried out in eight forest fragments ranging from 0.25 to 200 ha embedded in a matrix of flooded savanna in the Arauca municipality ( fig. 1). Altitudes within the study area range from 125 to 130 m a.s.l., with an unimodal eight-month rainy season between April and November (95% of yearly precipitation), and a dry season from December to March. The average annual rainfall is 2,200 mm with relative humidity between 65% for the dry season and 80% for the rainy season (Rippstein et al., 2001).

Field and laboratory work
A modification of the ALL protocol (Ants of the Leaf Litter protocol) was used in each of the eight selected areas to rapidly assess and record a high percentage of ant species in a short period of time (Agosti & Alonso, 2003). In each forest fragment sampled, we used a transect of 190 m, perpendicular to the edge of the forest as reference, and in each transect, we arranged seven sampling points every 20 m. Thus, three of the sampling points were located in the flooded savannah, one on the edge and three inside the forest patch. Three ant capture techniques were used at each sampling point: first, a pit-fall trap barley with 7 g of protein was installed for 24 hours; second, a sample of 1 m 2 of litter was collected, sieved and processed in a Winkler bag; and third, direct capture was performed at each sampling point for ten minutes using entomological forceps and aspirators.
The samples were transported to the Colección Entomológica de la Orinoquia (CEO) (Entomologic Collection of the Orinoquia) of the Orinoquia campus at the Universidad Na� cional de Colombia for separation, cleaning and taxonomic identification of the specimens. We used the taxonomic keys of Bolton (1994), Schmidt &Shattuck (2014) andFernández (2003) to identify specimens to the subfamily and genus level; while the taxonomic keys of Brown (1976, 1978), Fernández (1991), Jiménez et al. (2007 and MacKay & Mackay (2010) were used to identify species level.
A range-abundance plot was used to assess the evenness of the hunting ant commu� nity. Based on species abundances collected during the study, species were classified as abundant (more than 30 specimens captured), intermediate (between 30 and five specimens collected) or rare (with less than five specimens collected).
In terms of spatial distribution of the species in the gradient forest, edges, and flooded Compared with other departments of the Colombian Orinoquia region, the species richness of hunting ants (15 species) in Arauca is higher than in Casanare department (10 species), sharing three species, Neoponera villosa, Neoponera verenae and Neoponera apicalis (Ji� ménez et al., 2007). However, Arauca species richness is lower than that in the Guaviare department (19 species) and Vichada (17 species The large variations in species richness across Orinoquia departments suggest that the biodiversity of hunting ants is presently underestimated, probably due to two factors. The first of these is the low number of ants shared by Arauca and Casanare departments, despite their geographical proximity and the similarity of their ecosystems. The second factor is that the much higher value (55 species) reported for the Meta department probably reflects higher sampling effort and research there due to the area's proximity to cities that have institutions concerned with biodiversity studies (Fernández, 2003;Jiménez et al., 2007;Sanabria-Blandón & Chacón de Ulloa, 2011;Chávez et al., 2008;Abadía et al., 2010).
The first record for Colombia of T. cf. mutilatus may have implications in many biologi� cal aspects. First, it confirms the prediction that the mutilatus complex occurs not only in savannas in the southern Amazon basin (i.e. as the Cerrado and the Catinga between the 3°S y 29°S), but also in the Orinoquia biogeographical region of Colombia and Venezuela (Helobioma Amazonia-Orinoquia) (Jahyny, 2010;Jahyny et al., 2015). Second, it shows that there should be a taxonomic revision of the genus since there are sporadic new records in the neotropical region of probable new species that are not fully described and classified. This results in difficulties in reaching a consensus on species number in this taxonomic complex (Delabie, personal communication).
The results of our study support the Lozano-Zambrano & Fernández (2007) statement suggesting that hunting ants are still poorly studied in some areas of Colombia. This study is the first approach to determine the distribution of hunting ant species in the northern part of the Colombian Orinoquia region, and the findings broaden the geographical distribution of 14 species for Colombia and one species (T. cf. mutilatus) for South America.