Estructura poblacional de dos especies de dichotomius hope, 1838 (Coleoptera: Scarabaeinae) en un paisaje cafetero de los andes occidentales de Colombia, Risaralda

Abstract

Dung beetles are a group of insects widely recognized as ecological indicators of anthropic disturbance, reason why they count with a lot of information at the level of the assemblies. In contrast, population-based studies are still scarce and little has been understood on how fragmentation and transformation of their habitats affect the structure and dynamics of Scarabaeinae populations. Some aspects of the population structure of two typical Scarabaeinae species (Dichotomius cf. satanas and D. cf. alyattes) of the coffee landscape in the Western Andes of Colombia are examined in this paper. Between August 2010 and February 2011, six ecotone transects, each one consisting of 15 non-lethal pitfall traps, primed with a mixture of human and pig excrement, were installed in two coffee growing locations of Risaralda. Each month the traps were active for 48 hours and were inspected every 24 hours. Specimens of both species were labeled with the elytron drilling method in each inspection. A total of 1723 individuals were marked of which 73 were recaptured (43 D. cf. alyattes and 30 D. cf. satanas). The estimated population size differed between species and locations, and the average density ranged between 26.4 and 172.2 ind/km2. Both species had similar gender ratio (~1:1) and showed differences in their habitat preferences: D. cf. satanas tended to stay inside the forest, while D. cf. alyattes used extensively ecotone forest - sun coffee.