A reappraisal of the ‘Fracticornis–Opacicollis' taxonomic complex of the genus Onthophagus Latreille using allozymes (Coleoptera, Scarabaeoidea)

The present taxonomic status of the so called fracticornis–opacicollis complex of the genus Onthophagus, Onthophagus fracticornis (Preyssler, 1790), Onthophagus similis (Scriba, 1790) and Onthophagus opacicollis Reitter, 1892 is still controversial. Discrepancies mainly involve the status of O. similis and O. opacicollis. A genetic analysis of nine populations of this complex using eight loci is presented, indicating that: (i) O. fracticornis is a good species, and (ii) the genetic distances between O. opacicollis and O. similis populations as a function of the biogeographic scenery (allopatry versus sympatry), indicate that they are not completely reproductively isolated across their entire geographic range, thus suggesting a still unfinished speciation in different areas. The data demonstrate both the existence of some gene flow between O. opacicollis and O. similis in one place (‘El Barraco’; Central Spain) and isolation in others (‘Sa Nevada’; South-east Spain). Geographic areas hosting populations of both taxa with intermediate genetic distances (‘Doñana’; South-west Spain) also exist in the Iberian Peninsula.