Extreme trophic and habitat specialization by Peruvian dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae)

Resource partitioning strategies can help us understand the origin and maintenance of highly diverse communities. We collected 205 dung beetle species (Coleoptera: Scarabaeidae: Scarabaeinae) associated with many different kinds of resources in southeastern Peru. We focus only on extreme cases of resource specialization of species occupying unusually narrow ecological niches, rather than the broad range of specialists which exists. The natural history of most of these species is previously unknown, and several have been considered very rare. Although dung beetles were captured with all types of dung, including avian, reptile and invertebrate dung, species did not specialize exclusively on certain dung types. Ten species appeared to specialize exclusively on a single non-dung food resource, including fruit, fungus, carrion, dead invertebrates, and live millipedes. The diets of 15 species captured only by hand or with passive flight intercept traps are unknown, and these included species in unusual genera such as Anomiopus, Bdelyrus, Canthonella, Dendropaemon, and Sinapisoma. Eleven species appeared to specialize exclusively on a restricted habitat or microhabitat such as riverine beach, Guadua bamboo patches, river alder forest (Tessaria), attine ant nests, or abandoned termite nests. Four species of Canthon were forest canopy specialists. The apparent rarity of some of these species, such as Canthonidia rubromaculata Blanchard, Deltochilum valgum Burmeister, Ontherus laminifer Balthasar, and Ontherus raptor Génier, may only be due to their unusual habits, while other species, such as Megatharsis buckleyi Waterhouse, appear to be genuinely rare. We also discuss the implications of these findings for sampling methodology and assessment of species abundance distributions.