Search

Digitonthophagus gazella, a dung beetle of Indoafrican origin was first introduced to the Americas in the 1970s. Since then it has increased its range through deliberate introductions by national programs and by natural spread in the absence of geographical barriers. The species continues to expand its range as it invades new regions following the anthropogenic clearing of forests. We present the first reports of D. gazella in Peru and indicate that the species is now, perhaps, the most widespread dung beetle in tropical and subtropical pastures. [ABSTRACT FROM AUTHOR]

This study examines the effects of deforestation, and the habitat value of coffee and regenerated forest for tropical dung beetles, a functionally significant insect group. Pitfall trapping was conducted at 22 sites in a montane region of central Peru during April and November/December of 2002. Sites included primary and secondary forest, shadecoffee, regenerated forest and open farms (mainly with banana, yuca, and corn). Ordination techniques indicated that beetle assemblages in forests, regenerated forest and coffee were relatively similar. However, assemblage compositions in forested areas differed even at similar altitudes under the influence of biogeographical factors, and the assemblages at disturbed sites (farms/coffee) were influenced by beetle dispersal from adjacent forests. During dry months, when beetle activity is low, communities at all habitat types tended to converge because fewer unique species were recorded in forests at that time and habitat/ season generalists were dominant. Preliminary results also indicate that beetles in shady crops such as bananas responded to plant growth: as the banana canopy closed-in, producing more shade, open-habitat specialists retreated and forest/shade specialists invaded the sites. Chronosequence data at two of the sites demonstrate the rapid and dramatic changes in species richness and assemblage composition caused by deforestation. As forests become increasingly fragmented, and open farms continue to expand, dung beetles will become more restricted to the remaining fragments and reserves. In the mosaic landscape studied here, shade crops, like coffee, act as habitat and corridors for many dung beetle species. Small farm size and the consequent magnitude of edge effects, likely contributed to beetle movement between habitat types and determined the apparent generalist nature of many of the dung beetle species in this study. [ABSTRACT FROM AUTHOR]

This study examines the effects of resource distribution on colonisation, intra- and interspecific aggregation, and the occurrence of low-density, competition refuges for tropical dung beetles. In field experiments from central Peru, using dung pats (resource patches) of different volumes, the numbers of interacting species and total beetle biomass at individual pats increased with increasing pat volume. In two of three separate experiments (including an experiment that also varied patch density), this represented a decrease in the biomass of beetles per unit volume (biomass-density) at larger patches. The numbers of interacting tunneller species and tunneller biomass-density were also related to the distance between pats (patch density) in one of two experiments with constant numbers of pats. Closely positioned pats had generally fewer interacting species and a lower biomass-density of beetles. For the most abundant Dichotomius species, interspecific associations increased as distances increased between dung pats. The numbers of interacting species and biomass-density declined linearly under the combined effects of increasing patch density and local patch abundance in 25 m2 plots. In experimentally placed grids with large numbers of pats, colonisation of pats at the edge of the grids was generally higher than at the centre of the grids for tunnellers and Eurysternus spp. but not for ball rollers; however, at least tunnellers did not readjust to avoid patches with high densities of competitors. These results indicate that an aggregated distribution of dung and natural variability in patch size contribute to species coexistence by creating low-density refuges for weaker competitors. [ABSTRACT FROM AUTHOR]