Spatial and Temporal Variation of Dung Beetle Assemblages in a Fragmented Landscape at Eastern Humid Chaco

Abstract

The aims of this study were to characterize the fauna of dung beetles and analyze their spatial and temporal diversity in a cattle ranch in the province of Chaco. Seven surveys were conducted in three environmental units: a forest fragment, a cattle pasture, and an open grassland. The efficiency of the sampling was assessed with non-parametric richness estimators, and attributes of the assemblage were evaluated. The species composition and the abundance distribution in each of the environmental units studied were compared using rank-abundance curves. The indicator value of each species was measured with the IndVal method. The relationship between richness, abundance, and environmental variables (temperature, precipitation, and relative humidity) was calculated by multivariate multiple regression analysis. A total of 3,356 adult individuals belonging to 29 species of the subfamily Scarabaeinae and to five species of Aphodiinae were captured. Dichotomius nisus (Olivier), Trichillum externepunctatum (Preudhomme), Canthon podagricus (Harold), Onthophagus hirculus (Mannerheim), Pseudocanthon aff. perplexus, Ontherus sulcator (Fabricius), and Ataenius platensis (Blanchard) were the most abundant. Diversity, species richness, and abundance were highest in the forest fragment and in spring and summer captures. Between 94% and 97% of the species present in the entire landscape were recorded. According to the analysis of similarity, the composition of the assemblage was different among habitats. Eurysternus caribaeus (Herbst), Eurysternus aeneus (Génier), and O. sulcator were indicators of the forest. In the three units, the coprophagous species represented more than 60% of the total species number. The rainfall regime, the temperature, and the heterogeneous use of the environmental units influenced the structure of dung beetle assemblages.

First report on dung beetles in intra-Amazonian savannahs in Roraima, Brazil

“…Most species we found belong to species-clusters that have been collected within dry, open and highly disturbed environments on the American continent, some of them with records from Argentina (Damborsky et al 2015), Mexico (Novelo et al 2007), Ecuador (Carpio et al 2009), Venezuela (Lozano 2010), Colombia (Noriega et al 2007) and Costa Rica (Padilla-Gil & , coastal low land forests ('Tabuleiro' forests) (Endres et al 2007) and native and exotic pasturelands (Almeida et al 2011, Costa et al 2009. In addition, the species reported here were also found within highly impacted Brazilian forests, such as northeastern fragments of Atlantic forest (Salomã o & Iannuzzi 2015, Viegas et al 2014, planted Eucalyptus sp.…”

“…Those species have been considered as coprophagous and generalist (Hernandéz 2007, collected by pitfall traps baited with different types of dung, rotting fruits and carcass , Flechtmann et al 2009, Puker et al 2013, Rosa et al 2011, Silva et al 2008). This species-complex have been recorded in South American open areas at altitudes o1000 m, such as Argentinian Chaco (Damborsky et al 2015), Colombian secondary dry forests (Noriega et al 2007) and Bolivian transitional forests (Vidaurre et al 2008). In Brazil, they have been collected within pasturelands (Puker et al 2013, Silva et al 2014, caatinga (Hernandéz 2007, Santos et al 2014, Silva et al 2007, Vieira & Silva 2012) and restinga areas , Vieira et al 2008).…”

“…Dichotomius nisus (Olivier 1789) ( Figure 1F) is considered a nocturnal coprophagous-generalist species (Hernandéz 2007, Silva et al 2007, Vieira et al 2008, commonly occurring within opened and/or disturbed environments (Filgueiras et al 2015, Nunes et al 2012. It is widely distributed, with records from Guyana (Boilly & Vaz-de-Mello 2014), Argentinian Chaco (Damborsky et al 2015), transitional forests in Bolivia (Vidaurre et al 2008), Colombia Andes (Putumayo region) (Escobar et al 2005) and Venezuelan dry forests and pastures (Ferrer-Paris et al 2013, Lozano 2010. In Brazil, it has been sampled with both dung and carrion-baited pitfall traps within more than 17 states (Louzada et al 2007).…”

Escarabajos copronecrófagos (Scarabaeidae: Scarabaeinae) de la Reserva Natural Educativa Colonia Benítez, Chaco, Argentina

“…Ontherus sulcator fue la única especie recolectada en todos los meses muestreados, con trampas de caída y trampas de luz; la atracción de esta especie hacia la luz artificial también es citada por Génier (1996). Cabrera-Walsh y Gandolfo (1996) identifican esta especie como representativa de los ambientes ganaderos del centro de Argentina, aunque también se cita en bosques de la región Neotropical (Campos y Hernández, 2013;Damborsky, Álvarez-Bohle, Ibarra-Polesel, Porcel y Fontana, 2015). Favila (2005) afirma que los fragmentos de bosque menores a 10 ha son invadidos por especies de pastizales circundantes; no es extraño entonces la presencia de O. sulcator en ambientes boscosos de la RNECB.…”

“…No se registró correlación entre la composición del ensamble y las precipitaciones. Resultados similares han sido encontrados por Orozco y Pérez (2008) en 2 bosques (seco premontano y montañoso húmedo), aunque difieren con los de otros autores (Barbosa- Silva, Hernández, Ide y Moura, 2007;Bustos-Gómez y Lopera-Toro, 2003;Damborsky et al, 2015;Martínez, 2010;Milhomem, Vaz de Melo y Diniz, 2003) quienes encontraron la mayor riqueza y abundancia de especies durante los periodos lluviosos. Escobar (2000) destaca que las variaciones de la comunidad de escarabajos coprófagos entre periodos dependen también de los ambientes, y no encuentra relación entre la riqueza y los niveles de precipitación en bosques de montaña.…”