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 andanalyze their spatial and temporal diversity in a cattle ranch in the provinceof Chaco. Seven surveys were conducted in three environmental units: aforest fragment, a cattle pasture, and an open grassland. The efficiency ofthe sampling was assessed with non-parametric richness estimators, andattributes of the assemblage were evaluated. The species composition andthe abundance distribution in each of the environmental units studied werecompared using rank-abundance curves. The indicator value of each specieswas measured with the IndVal method. The relationship between richness,abundance, and environmental variables (temperature, precipitation, andrelative humidity) was calculated by multivariate multiple regression analysis.A total of 3,356 adult individuals belonging to 29 species of the subfamilyScarabaeinae and to five species of Aphodiinae were captured. Dichotomiusnisus (Olivier), Trichillum externepunctatum (Preudhomme), Canthonpodagricus (Harold), Onthophagus hirculus (Mannerheim), Pseudocanthonaff. perplexus, Ontherus sulcator (Fabricius), and Ataenius platensis(Blanchard) were the most abundant. Diversity, species richness, and abundancewere highest in the forest fragment and in spring and summercaptures. Between 94% and 97% of the species present in the entirelandscape were recorded. According to the analysis of similarity, the compositionof the assemblage was different among habitats. Eurysternuscaribaeus (Herbst), Eurysternus aeneus (Génier), and O. sulcator wereindicators of the forest. In the three units, the coprophagous speciesrepresented more than 60% of the total species number. The rainfallregime, the temperature, and the heterogeneous use of the environmentalunits influenced the structure of dung beetle assemblages.