Multiple new species: Cryptic diversity in the widespread mite species Cymbaeremaeus cymba (Oribatida, Cymbaeremaeidae).

The absence of obvious morphological differences between species impedes species identification in many groups of organisms. Such cryptic species appear to be particularly common in small-bodied animals, impacting species richness estimates. In this study we aimed at characterizing the molecular diversity of the Palearctic arboreal oribatid mite species Cymbaeremaeus cymba across large parts of Europe. Phylogenetic analyses of three molecular markers, including the COI barcoding region, identified eight well supported, fairly divergent clades within C. cymba, which we consider to represent distinct species based on molecular species delimitation methods. Intraspecific variation of the COI gene was extremely low in all putative species, contradicting previous assumptions of high intraspecific diversity in oribatid mites. The frequent co-occurrence of two species on a single tree suggests an ecological micro-niche differentiation. Contrary to previous studies on oribatid mites, we find that COI is a good marker for species delimitation and its further use for barcoding of oribatids is highly recommended. Furthermore, we provide descriptions of six new Cymbaeremaeus species and designate a neotype of C. cymba.