Ecology and Biogeography of Dung-Beetle Communities (Coleoptera, Scarabaeoidea) in an Iberian Mountain Range

Abstract

The role of the Eastern Mountains of the Iberian Central System (EMICS) as both a barrier to the dispersion of, and ecologic refuge for, Scarabaeoidea dung beetles is studied. An Ecogeographic Patterns comparison method (EP = set of ecologic features common to, and present geographic range shared by, a group of species) to weight the historical and ecological causes of geographic distribution is proposed. This method is based on the assumption that species now sharing geographic ranges, with common structural and nonstructural features, also have a (to some extent) common evolutionary history. The data studied indicate that (i) fauna of the N and S slopes are identical. Euroturanian and Mediterranean species, and those which belong to the Scarabaeidae family, predominated in all samples. Except for very few species, the EMICS have not impeded dispersal of Scarabaeoidea dung beetles; minor regional differences should be explained in terms of ecological causes. (ii) The variation in abundance, richness, characteristic species, systematic composition and EP was found to relate mainly with altitude. Principally endemic, European or wider-range species of the Aphodiidae and Geotrupidae families, prevented from dispersing toward lower altitudes by a climatic discontinuity, colonize the higher altitudes, having taken refuge in the EMICS after Pleistocene glaciations. (iii) The explanation of the causes of the present vertical distribution of Scarabaeoidea dung beetles in the EMICS must take into account the historical events there, and major modifications of the geographic distribution of the species inhabiting it. The agreement of inferences drawn from EP analysis with those drawn from paleontologic and phylogenetic evidence (for some species) supports the use of EP, and validates the assumption made in their application.