How a locality can have so many species? A case study with dung beetles (Coleoptera: Scarabaeinae) in a tropical rain forest in Colombia

Dung beetles of the subfamily Scarabaeinae (Coleoptera: Scarabaeidae) are one of the most important insect groups in tropical regions because their relevant ecosystem role as organic recycling agents, biological pest controllers and secondary seed dispersers. However, our knowledge of the different mechanisms that maintain assemblage structure and allow species coexistence is poor. We lack such information because dung beetle assemblages are often sampled over the short term, there are few studies that cover extended periods of time and broad spatial areas, and it is common to use just one type of trap and bait. To better explore the mechanisms underlying dung beetle coexistence, it was studied a beetle assemblage found in a tropical rain forest located in Tinigua National Park in Colombia. Sampling was conducted in August 1992, May-July and December 1994, January and December 1995, January and July 1996, January-July 1997, and January and July 1998. Dung beetles were sampled in the three main habitats found in the study area: mature mainland forest, flooded lowland forest, and river beaches. Specimens were collected using baited pitfall traps, flight interception traps, and baited elevated traps placed at different heights using different type of baits. In addition, feces from different vertebrates, vegetation, logs, fungi, litter, and fallen fruit were checked for the presence of dung beetles. A total of 70 species belonging to 19 genera and 7 tribes were collected. Compared to other areas, previously sampled in Colombia, this area demonstrates a remarkable diversity and has a very high level of species richness (one of the highest in the country). Nevertheless, it cannot be considered a hotspot for endemism because there is a strong influence and contribution of species of nearby biogeographic provinces to its own fauna. Some of the mechanisms that may affect the richness and structure of the assemblage, favoring the coexistence of species are: spatial partitioning (habitats and microhabitats), temporal partitioning (seasonality and dial activity), resource partitioning, and guild-specific resource relocation behavior. The values of the Jaccard similarity index reveal low levels of species overlap. Therefore, these coexistence mechanisms appear to act in tandem to partition the ecosystem in a way that decreases overlap among similar species, thus allowing a large number of dung beetle species to coexist in the same area. These results demonstrate that it is necessary to carry out broad-ranging and exhaustive sampling to fully characterize the structure of tropical dung beetle assemblages. Finally, to completely describe the assemblage composition at this locality, the following additional improvements should be made to the sampling protocol: carrying out exhaustive sampling over one full year; using more specialized baits; studying the forest canopy; searching in specialized microhabitats, such as bromeliads and ant and termite nests; and characterizing potential phoretic interactions with mammals. © 2015 by Nova Science Publishers, Inc. All rights reserved.