Making the cryptic visible – resolving the species complex of A phodius fimetarius ( L innaeus) and A phodius pedellus (de G eer) ( C oleoptera: Scarabaeidae) by three complementary methods

Species in cryptic complexes are, per definition, difficult to identify using morphological characters. One such complex was recently detected in the dung beetle A phodius fimetarius ( L innaeus) sensu lato, an abundant dung beetle with a wide distribution. While the two component taxa, A phodius fimetarius sensu stricto and A phodius pedellus (De G eer) exhibit distinctly different karyotypes, the validity of subtle morphological characters proposed to distinguish between them has been debated. Given the variability and minor interspecific differences in external characters, the large‐scale distribution of respective taxa has remained unknown, as have potential differences in ecology and habits. In this study, we ask how A. fimetarius and A. pedellus can best be distinguished, whether the use of different types of characters (karyotypes, DNA sequences and morphological traits) results in consistent species identification, where these species occur and whether they exhibit ecological differences. In total, we inspected a material of 4401 individuals from across the globe, of which 183 were examined for both mtDNA sequences and morphology, 154 for both morphology and karyotype, and 9 (including the recently proposed neotype of Aphodius fimetarius ) for all three types of characters. As a marker gene, we sequenced a 590 bp region of the cytochrome c oxidase I gene for 183 individuals. Overall, DNA sequences offered a clear‐cut distinction between taxa: sequences of A. fimetarius and A. pedellus differed by an average pairwise distance of 8.2%, whereas variation within species was only 0.9% for A. fimetarius and 0.5% for A. pedellus . Morphological and chromosomal characters offered species identifications consistent with that of molecular characters: karyotypes identified as A. pedellus consistently fell within one of the molecular clades, whereas karyotypes identified as A. fimetarius fell within the other clade. Likewise, the majority of individuals identified by morphological characters were assigned to the same species by sequence‐based characters. Both taxa thus defined were found to be H olarctic in distribution, with major sympatry within C entral and S outhern E urope and mixed patterns of sympatry within the US . Northern areas of E urope, A sia and N orth A merica are dominated by A. pedellus alone. Within A. pedellus , patterns of sequence diversity were indicative of a recent population expansion. In the western US , the phenology of a population