Biodiversitat, Ponerinae, Orinòquia, Biogeografia
Data de recepció: 20/03/17 | Data d'acceptació: 04/08/17 | Data de publicació: 08/09/17
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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 1m2 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.
Data published through GBIF and SiB Colombia (doi: 10.15472/vp8v42).
Key words: Biodiversity, Ponerinae, Orinoco, Biogeography
Nuevos registros de hormigas cazadoras (Poneroides y Ectatomminoides) en el norte de la Orinoquia Colombiana.
Se revisaron 466 especímenes de hormigas cazadoras recolectadas en ambientes de sabana inundable y bosques en la zona rural del municipio de Arauca (Arauca, Colombia). En ocho zonas de bosque con tamaños de entre 0,25 y 220 ha se ubicó un transecto lineal con siete puntos de muestreo separados por 20 m con una superficie de 10 m2 cada uno. En cada punto de muestreo se utilizaron tres tipos de técnicas: una trampa de caída por 24 horas, una muestra de 1 m2 de hojarasca procesada en saco mini Winkler y la captura directa. Se registraron 15 especies siendo el género más diverso Neoponera, con seis especies, seguido de Odontomachus, con dos especies, y Ectatomma, Anochetus, Gnamptogenys, Prionopelta, Pseudoponera, Pachycondyla y Thaumatomyrmex, con una sola especie cada uno. En este estudio se amplía la distribución geográfica de 15 especies para el norte de la Orinoquia colombiana y se registra por primera vez la presencia de Thaumatomyrmex cf. mutilatus en Colombia.
Datos publicados en GBIF y en SiB Colombia (doi: 10.15472/vp8v42).
Palabras clave: Biodiversidad, Ponerinae, Orinoquia, Biogeografía
Nous registres de formigues caçadores (Poneroides i Ectatomminoides) al nord de l’Orinòquia Colombiana.
Es van revisar 466 espècimens de formigues caçadores recol·lectades en ambients de sabana inundable i boscos a la zona rural del municipi d’Arauca (Arauca, Colòmbia). En vuit zones de bosc amb grandàries de 0,25 a 220 ha es va situar un transsecte lineal amb set punts de mostreig separats per 20 m amb una superfície de 10 m2 cadascun. En cada punt de mostreig es van utilitzar tres tipus de tècniques: una trampa de caiguda per 24 hores, una mostra d’1 m2 de fullaraca processada en sac mini Winkler i la captura directa. Es van registrar 15 espècies, entre les quals el gènere més divers va ser Neoponera, amb sis espècies, seguit d’Odontomachus, amb dues espècies i Ectatomma, Anochetus, Gnamptogenys,Prionopelta, Pseudoponera, Pachycondyla i Thaumatomyrmex,
amb una sola espècie cadascun. En aquest estudi s’amplia la distribució geogràfica de 15 espècies per al nord de l’Orinòquia colombiana i es registra per primera vegada la presència de Thaumatomyrmex cf. mutilatus a Colòmbia.
Dades publicades a GBIF i a SiB Colombia (doi: 10.15472/vp8v42).
Paraules clau: Biodiversitat, Ponerinae, Orinòquia, Biogeografia
The Orinoquia region has an area of 251.185 km2 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 proximity 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 invertebrate 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 environments (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.
Material and methods
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 7g of protein was installed for 24 hours; second, a sample of 1 m2 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 Nacional de Colombia for separation, cleaning and taxonomic identification of the specimens. We used the taxonomic keys of Bolton (1994), Schmidt & Shattuck (2014) and Fernández (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 community. 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).
Using the three sampling methods we collected 30,496 specimens of the Formicidae family. Of these, 466 were hunting ants and they were assigned in three subfamilies (Ponerinae, Amblyoponinae and Ectatomminae), three tribes, nine genus, and 15 species, using the taxonomy proposed by Schmidt & Shattuck (2014), Bolton (2003) and Brady et al. (2006) (table 1). Appendix 1 shows detailed information about location and habitat type of all specimens. The data set cited in this work could be consulted in GBIF and in SiB Colombia (doi: 10.15472/vp8v42).
The genus Neoponera had the highest species richness with six species, followed by Odontomachus with two species. The genus Prionopelta, Anochetus, Pachycondyla, Pseudoponera, Thaumatomyrmex, Ectatomma and Gnamptogenys were each represented only by one species. The species with highest abundances were Ectatomma ruidum Roger, 1861 with 51.9% (242) and Odontomachus bauri Emery, 1892 with 28.8% (134). Intermediate abundances were recorded for Pachycondyla harpax (Fabricius, 1804) 6,8% (32) and Neoponera verenae Forel 1922 with 4.9% (23). The other eleven species had abundances lower than 4% and were considered rare species (fig. 2).
In terms of spatial distribution of the species in the gradient forest, edges, and flooded savanna matrix, the most abundant species E. ruidum and O. bauri were found in all three habitats (table 1), probably because they are generalist and can occupy different habitats. Habitat preferences by lesser abundant species were variable While P. harpax was found in all three habitats, N. verenae was only found in forest fragments and edges. Finally, rare species showed affinity for forest and edges, but not for savanna (table 1).
Hunting ant studies across different successional stages and landscapes in Colombia show that species richness in forests is higher than in savanna ecosystems. This trend is attributed to higher vegetation coverage favouring higher microhabitat availability (Serna & Vergara-Navarro, 2008; Chavez et al., 2008; Abadía et al., 2010; Sanabria-Blandón & Chacón de Ulloa, 2011).
This study broadens the geographical distribution of 15 hunting ants species collected in the Orinoquia. Four of these species were previously documented for the Colombian Amazonian: Neoponera foetida (Linnaeus, 1758) and Neoponera goeldii Forel, 1912 previously found only in Amazonas department (Jiménez et al., 2007); Prionopelta amabilis Borgmeier, 1949 for the Amazonas and Caquetá departments (Jiménez et al., 2007); and Neoponera unidentata Mayr, 1862 for all the Colombian Amazonian region except Vaupés department (Jiménez et al., 2007). Finally, this is the first report for Thaumatomyrmex cf. mutilatus Mayr, 1887 in Colombia, a species previously documented in Brazil (southern of the Amazon basin), northern Argentina and Paraguay (Jahyny et al., 2008).
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 (Jiménez et al., 2007). However, Arauca species richness is lower than that in the Guaviare department (19 species) and Vichada (17 species) (Jiménez et al., 2007) with which Arauca shares four and five species respectively. For the Meta department, 55 species have been reported (Jiménez et al., 2007), nine of which are shared with the Arauca department.
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 rank-abundance relationship indicates that E. ruidum, O. bauri, and P. harpax are the dominant species in the hunting ant community. These species were collected in the three habitats, confirming their generalist ecology as reported by many authors (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 biological 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.
The authors of this paper wish to express their gratitude to a Jacques Hubert Charles Delabie (Departamento de Ciências Agrárias e Ambientais de la Universidade Estadual de Santa Cruz UESC), Benoit Jean Bernard Jahyny (Universidade Federal do Vale do São Francisco–UNIVASF) and William P. Mackay (Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso) for their assistance in the confirmation and identification of some of the specimens cited in this publication and their valuable bibliographic contributions. We also thank the interns Evelyn Gómez Tapia and Ana María Romero and students Maikol Jiménez, Sebastián Peralta and Carlos Gamba for their collaboration in the phases of field work, cleaning and organizing the collected entomological material. Pilar Angulo-Sandoval kindly reviewed the English version of this manuscript. Financial support for this project came from the ‘Convocatoria de Investigación para Financiar Pasantías, Trabajos de Grado en Pregrado o Posgrado en Temáticas Relacionadas con la Orinoquia 2013 II’ from the Sede Orinoquia-Universidad Nacional de Colombia. We thank the owners of the areas where the ant collections were conducted: Juan Carlos Castañeda Forero, Santiago Cuenza, the Garcés Bona family, Jairo Dario Piedrahita Sabogal, and Luis Ernesto Rodríguez Cuenza.