Changes in the structure of Melolonthidae (Coleoptera: Scarabaeoidea) assemblages along a temporal gradient in a natural reserve in Chaco, Argentina

Abstract

Melolonthidae beetles have been proposed as bioindicators because of their important role in the ecosystem and sensitivity to disturbance processes. However, the assemblage structure of these species in Argentina is unknown. In this study, the first attempt at determining Melolonthidae diversity, we analysed the abundance and diversity of the Melolonthidae assemblage and the species richness turnover over a period of three years. We collected samples in a gallery forest relict of a small protected area in which two light traps were installed. We collected a total of 474 specimens belonging to 38 species, two of which are new records for Argentina. The assemblage was characterised by numerous rare species, and the richness and diversity as well as the distribution of species abundance varied over the three years of the study. Replacement values varied based on the similarity indices that were used. Selected environmental variables (relative humidity, temperature and rainfall) were correlated with the richness and the abundance of the beetles. Our results suggest that the community of Melolonthidae could be considered dynamic, even over relatively short periods of time. Rare species play a major role in analyses of the similarity between assemblages and could suggest exaggerated turnover values. The high richness of the study area may be due to its good state of preservation or to its small area, which allows the entry of species from surrounding environments, showing how complex and fluid the Melolonthidae community can be in small patches of forest.