Recambio altitudinal, estructura funcional y tasas de remoción del ensamble de escarabajos coprófagos (Coleoptera: Scarabaeidae) en la Sierra Nevada de Santa Marta, Magdalena, Colombia

Abstract

Diversity gradients on mountains have great potential to improve our understanding of species distribution, richness patterns, and conservation, allowing us to generalize patterns of spatial dynamics associated with increasing altitude. Dung beetles are currently recognized as bioindicators that fulfill diverse functions in the ecosystem such as secondary seed dispersal, microorganism suppression, dung removal, and soil fertilization, among others. The Sierra Nevada de Santa Marta (SNSM) in Colombia is a peripheral mountain system with ideal conditions for studying altitudinal gradients. The present study evaluated the structure, composition, functional diversity, and dung removal rates of the dung beetle (Coleoptera: Scarabaeidae) assemblage along the northwestern slope of the SNSM. Sampling was carried out between December and January of 2020. Collections were made at seven stations, from 400 to 2830 m a.s.l. using pitfall traps placed in linear transects separated by 50 m from each other and approximately 400 m between each location. For the analyses of functional diversity, 12 morphological and ethological traits were measured. For the excrement removal rates, an experiment was carried out at the same heights for 24 hours before sampling. The structure and composition of the assemblage of dung beetles and their relationship with the altitudinal gradient were analyzed, taking into account biological and ecological aspects. For this, rarefaction curves, functional diversity indices, dissimilarity indices, non-metric multidimensional scaling, and a Mantel test were used. A total of 4792 specimens corresponding to 50 species, 18 genera, and 9 tribes were recorded. The richness, abundance, functional groups, and functional diversity markedly decrease with altitude, with significant differences between all localities. The structure and composition of the assemblage are represented by a marked pattern of replacement, with a marked difference between species from low, medium, and high zones. Regarding the removal rates of excrement, it was observed that they have a negative correlation with altitude as they decreased with the gradient. Additionally, it was found that at altitudes higher than 2032 m a.s.l. there is an abrupt drop in the removal of excrement, which is explained by the low richness, abundance, functional groups, and biomass found at these altitudes. Is confirmed that the SNSM is a system with a high species richness. Furthermore, the structure and composition of the dung beetle assemblage are characterized by several factors, including biogeographic, environmental, anthropogenic, and climate change aspects. It is essential that conservation plans must be structured, giving priority to the most diverse areas recorded here. It is recommended to evaluate functional processes and ecosystem services in other slopes of the SNSM and in other mountain systems, as well as to carry out studies using other groups of insects to find out how are structured and their contributions to the ecosystems. It is also essential to study different groups of vertebrates since they have an impact on the structure and composition of dung beetle assemblages.