The use of molecular genetic data in phylogenetic systematics has revolutionized this field of research in that several taxonomic groupings defined by traditional taxonomic approaches have been rejected by molecular data. The taxonomic classification of the oribatid mite group Circumdehiscentiae ("Higher Oribatida") is largely based on morphological characters and several different classification schemes, all based upon the validity of diagnostic morphological characters, have been proposed by various authors. The aims of this study were to test the appropriateness of the current taxonomic classification schemes for the Circumdehiscentiae and to trace the evolution of the main diagnostic traits (the four nymphal traits scalps, centrodorsal setae, sclerits and wrinkled cuticle plus octotaxic system and pteromorphs both in adults) on the basis of a molecular phylogenetic hypothesis by means of parsimony, likelihood and Bayesian approaches.

A challenge for taxonomists all over the world and across all taxonomic groups is recognizing and delimiting species, and cryptic species are even more challenging. However, an accurate identification is fundamental for all biological studies from ecology to conversation biology. We used a multidisciplinary approach including genetics as well as morphological and ecological data to assess if an easily recognizable, widely distributed and euryoecious mite taxon represents one and the same species. According to phylogenetic (based on mitochondrial and nuclear genes) and species delimitation analyses, five distinct putative species were detected and supported by high genetic distances. These genetic lineages correlate well with ecological data, and each species could be associated to its own (micro)habitat. Subsequently, slight morphological differences were found and provide additional evidence that five different species occur in Central and Southern Europe. The minuteness and the characteristic habitus ofCaleremaeus monilipestempted to neglect potential higher species diversity. This problem might concern several other “well-known” euryoecious microarthropods. Five new species of the genusCaleremaeusare described, namelyCaleremaeus mentobellussp. nov.,C. lignophilussp. nov.,C. alpinussp. nov.,C. elevatussp. nov., andC. hispanicussp. nov. Additionally, a morphological evaluation ofC. monilipesis presented.

The oil gland secretion profile of a cosmopolitan oribatid species, Trhypochthonius tectorum (Berlese) (Trhypochthoniidae), was investigated by gas chromatographic - mass spectrometric analyses and is shown to consist of 11 components, comprising four terpenes (neral, geranial, two isomeric farnesals), three hydrocarbons (pentadecane, a heptadecadiene and a heptadecene), two aromatic compounds (2-hydroxy-6-methylbenzaldehyde = 2,6-HMBD, γ-acaridial = 2-formyl-3-hydroxybenzaldehyde) and two components not yet identified. The stereochemistry of farnesals was partly elucidated, indicating the presence of (Z,?)-farnesal and (E,?)-farnesal, respectively. The unsaturated hydrocarbons were further characterised as 4-heptadecene and 6,9-hepadecadiene. The heptadecadiene and (Z,?)-farnesal represented the most abundant components, followed by 2,6-HMBD and γ-acaridial. (E,?)-farnesal, 4-heptadecene, pentadecane, neral and geranial were minor components. The oil gland secretion profile of T. tectorum is compared to secretion profiles of trhypochthoniid species from America and Japan, and possible (chemical) apomorphies of trhypochthoniid genera are discussed.

Though mostly soil dwelling, oribatid mites are found in all kind of habitats, with several species exclusively living on trees. Using previously published DNA sequences and eco-morphological data available from the literature, we inferred the number of transitions between soil dwelling to a truly arboreal lifestyle in oribatid mites and the shape evolution of a particular morphological structure of a sense organ (bothridial seta (= sensillus) of a trichobothrium), the shape of which was previously reported to be associated with an arboreal lifestyle. Our data suggest that a truly arboreal lifestyle evolved several times independently in oribatid mites, but much less often than previously proposed in the past. Even though all truly arboreal species indeed seem to possess a capitate sensillus, this character is not exclusive for arboreal taxa. Nonetheless, since all truly arboreal species do have a capitate sensillus, this might be considered an important (pre-)adaptation to a life on trees. We further provide guidelines on how the term “arboreal” should be applied in future mite research and emphasize the importance of exact microhabitat characterization, as this will greatly facilitate comparisons across studies.