Hidden biodiversity in microarthropods (Acari, Oribatida, Eremaeoidea, Caleremaeus).

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 of Caleremaeus monilipes tempted to neglect potential higher species diversity. This problem might concern several other "well-known" euryoecious microarthropods. Five new species of the genus Caleremaeus are described, namely Caleremaeus mentobellus sp. nov., C. lignophilus sp. nov., C. alpinus sp. nov., C. elevatus sp. nov., and C. hispanicus sp. nov. Additionally, a morphological evaluation of C. monilipes is presented.

Morphological analysis of the oribatid mite species Scutovertex pannonicus Schuster and description of its juvenile stages (Acari: Oribatida: Scutoverticidae).

This paper provides a detailed redescription of the adult as well as the first morphological description of all juvenile instars (inclusive egg, prelarva and earlier larval stages) of Scutovertex pannonicus. The adults are characterized by their relatively large size (692-892 µm), their well developed sharply bordered foveae which are regularly distributed on the whole notogaster, except in the central field and the posterior notogastral brush-like setae ps1, h1,-h3. The exochorion of the eggs shows the typical structures for the genus Scutovertex like 'mushrooms' and granules with the species-specific expression of the 'mushrooms' and its substructures. The exochorion is covered with an extra thin layer which is typical for this species. The larva and the nymphs can be distinguished from those of S. sculptus and S. minutus mainly by their lateral setae l' and l" on tibia I which are strongly serrated and slightly broadened.

Discrimination of Oribotritia species by oil gland chemistry (Acari, Oribatida).

The chemical composition of secretions from opisthonotal (oil) glands in four species of the oribatid mite genus Oribotritia (Mixonomata, Euphthiracaroidea, Oribotritiidae) was compared by means of gas chromatography--mass spectrometry. The secretions of all, O. banksi (from North America) and three Austrian oribotritiids (O. berlesei, O. hermanni, O. storkani), are shown to be based on certain unusual compounds, the iridoid monoterpenes chrysomelidial and epi-chrysomelidial and the diterpene ß-springene. These components probably represent general chemical characteristics of oribotriid oil glands. Their relative abundance in the secretions along with further components (mainly saturated and unsaturated C(13)-, C(15)-, C(17)-hydrocarbons, and the tentatively identified octadecadienal) led to well-distinguishable, species-specific oil gland secretions profiles. In addition a reduced set of "Astigmata compounds" (sensu Sakata and Norton in Int J Acarol 27:281-291, 2001)--namely the two monoterpenes neral and geranial--could be detected in extracts of O. banksi nevertheless indicating the classification of euphthiracaroids within the (monophyletic) group of "Astigmata compounds-bearing"-Oribatida. These compounds are considered to be apomorphically reduced in all Austrian species. Our findings emphasize the potential of chemosystematics using oil gland secretion profiles in the discrimination of morphologically very similar, syntopically living or even cryptic oribatid species.

Ancestral state reconstruction reveals multiple independent evolution of diagnostic morphological characters in the "Higher Oribatida" (Acari), conflicting with current classification schemes.

BACKGROUND: 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. RESULTS: The molecular phylogeny based on three nuclear markers (28S rDNA, ef-1alpha, hsp82) revealed considerable discrepancies to the traditional classification of the five "circumdehiscent" subdivisions, suggesting paraphyly of the three families Scutoverticidae, Ameronothridae, Cymbaeremaeidae and also of the genus Achipteria. Ancestral state reconstructions of six common diagnostic characters and statistical evaluation of alternative phylogenetic hypotheses also partially rejected the current morphology-based classification and suggested multiple convergent evolution (both gain and loss) of some traits, after a period of rapid cladogenesis, rendering several subgroups paraphyletic. CONCLUSIONS: Phylogenetic studies revealed non-monophyly of three families and one genus as a result of a lack of adequate synapomorphic morphological characters, calling for further detailed investigations in a framework of integrative taxonomy. Character histories of six morphological traits indicate that their evolution followed a rather complex pattern of multiple independent gains (and losses). Thus, the observed pattern largely conflicts with current morphological classifications of the Circumdehiscentiae, suggesting that the current taxonomic classification schemes are not appropriate, apart from a recently proposed subdivision into 24 superfamilies.

Phylogenetic analysis of European Scutovertex mites (Acari, Oribatida, Scutoverticidae) reveals paraphyly and cryptic diversity: A molecular genetic and morphological approach.

The soil and moss dwelling oribatid mite family Scutoverticidae is considered to represent an assemblage of distantly related but morphologically similar genera. We used nucleotide sequences of one mitochondrial (COI) and two nuclear (28S rDNA, ef-1alpha) genes, and 79 morphological characters to elucidate the phylogenetic relationships among 11 nominal plus two undescribed European mite species of the family Scutoverticidae with a particular focus on the genus Scutovertex. Both molecular genetic and morphological data revealed a paraphyletic genus Scutovertex, with S. pictus probably representing a distinct genus, and Provertex kuehnelti was confirmed as member of the family Scutoverticidae. Molecular genetic data confirmed several recently described Scutovertex species and thus the high species diversity within this genus in Europe and suggest that S. sculptus represents a complex of several cryptic species exhibiting marked genetic, but hardly any morphological divergence.

Ontogenetic changes in the chemistry and morphology of oil glands in Hermannia convexa (Acari: Oribatida).

As a first example for the chemistry of oil gland secretions in the Hermannioidea (one of the three superfamilies of desmonomatan Oribatida), the oil gland secretion of Hermannia convexa was investigated by gas chromatography-mass spectrometry. Hexane extracts of all juvenile stages showed a multicomponent chromatographic pattern, mainly consisting of well-known oil gland secretion components such as neral, geranial, gamma-acaridial and the unsaturated C17-hydrocarbons, 6,9-heptadecadiene and 8-heptadecene. The secretion profiles of juveniles varied slightly between samples of two different collections, namely in the presence of gamma-acaridial and 8-heptadecene. Furthermore, a minor component, identified as 1,8-cineole (= eucalyptol) and hitherto not known from oil gland secretions of other species, was recorded in both juvenile and adult extracts. In adult profiles, 1,8-cineole, in low amounts, represented the only detectable component; thus, their profiles fundamentally differed from those of juveniles. A subsequent histological investigation revealed well developed oil glands in all juvenile stages, but degenerated oil glands in adults, consistent with the chemical data. So far, apart from H. convexa, degeneration of oil glands in the course of ontogenetic development is only known from a brachypylid species; on the other hand, chemical oil gland-polymorphism between juveniles and adults may occur in closely related Nothridae while it does not occur in oil glands of early- and middle-derivative Oribatida (Parhyposomata, Mixonomata, trhypochthoniid Desmonomata), nor in astigmatid mites.