Effects of altitude and climatic variables on alpha and beta diversity of wood-degrading beetles (Coleoptera: Passalidae) in the Eastern Andes of Colombia

Abstract

Wood-degrading beetles are subsocial insects, with a primarily pantropical distribution. For most species, the entire life cycle occurs within a decaying log, where individuals feed and contribute to wood decomposition and nutrient recycling. Species tend to be restricted to particular altitudinal ranges, possibly due to variables involved in wood decomposition, including humidity and temperature. The objectives of this work were to evaluate the alpha and beta diversity of Passalidae across an altitudinal gradient in the Colombian Andes, to identify the environmental variables driving changes in alpha diversity, and to determine the processes structuring beta diversity. Beetles were sampled at four altitudes (2,500, 2,700, 3,000, and 3,300 m.a.s.l.) in the Municipal Natural Park Robledales de Tipacoque, Boyacá, Colombia, and temperature and humidity were recorded at each site. Overall, five passalid species were collected, with the highest abundance at 2,700 m.a.s.l., where Passalus curtus dominated; P. irregularis was most abundant at 2,500, P. curtus at 3,000, and P. quyefutynsuca at 3,300 m.a.s.l. There was a progressive decrease in diversity towards higher altitudes. Altitude, temperature, and humidity influenced alpha diversity, while beta diversity was structured by both the abundance gradient and the balanced variation in abundance components. In conclusion, altitude has an effect on the taxonomic diversity of wood-degrading beetles in the study area, and species distribution is influenced by the climatic variables, such as temperature and humidity, involved in the wood decomposition process.