Two new endemic species of scarab beetles are described from Costa Rica, Onthophagus humboldti sp. nov. and Uroxys bonplandi sp. nov. Onthophagus humboldti sp. nov. is also the tenth brachypterous Onthophagus species to be described worldwide, representing also a case of extreme brachyptery in Onthophagini. Illustrations for both new species, as well as marking differences with closely related species are included. Maps showing the distribution of the new species, as well as the distribution of brachypterous and endemic scarab-beetle species for Costa Rica are presented and discussed. The Cordillera de Talamanca represents an area where Scarabaeinae (four genera) show very high known levels of brachypterism in Mesoamerica. A reconstruction of the montane environment in the Cordillera de Talamanca during the Last Glacial Maximum (~24 ka) is analyzed, in order to try to understand a possible historical biogeography model that might promote high levels of brachypterism in scarab-beetles. The present study supports previous proposals that brachyptery is correlated with stable environments associated with deeply incised valleys. Tropical mountain ranges are also identified as having more endemics than lowland rain forests, contradicting accepted wisdom. Lastly, a mitochondrial DNA analysis supports the existence of the Onthophagus dicranius and the O. clypeatus species-groups as two well-defined and closely related branches.
Keywords: Biogeography; Cordillera de Talamanca; Last Glacial Maximum; boreotropical distribution; extreme brachyptery; mitochondrial DNA; paleogeography; refugia.
Bert Kohlmann, Ángel Solís, Guillermo Alvarado.