High-throughput DNA methods hold great promise for phylogenetic analysis of lineages that are difficult to study with conventional molecular and morphological approaches. The mites (Acari), and in particular the highly diverse soil-dwelling lineages, are among the least known branches of the metazoan Tree-of-Life. We extracted numerous minute mites from soils in an area of mixed forest and grassland in southern Iberia. Selected specimens representing the full morphological diversity were shotgun sequenced in bulk, followed by genome assembly of short reads from the mixture, which produced >100 mitochondrial genomes representing diverse acarine lineages. Phylogenetic analyses in combination with taxonomically limited mitogenomes available publicly resulted in plausible trees defining basal relationships of the Acari. Several critical nodes were supported by ancestral-state reconstructions of mitochondrial gene rearrangements. Molecular calibration placed the minimum age for the common ancestor of the superorder Acariformes, which includes most soil-dwelling mites, to the Cambrian–Ordovician (likely within 455–552 Ma), whereas the origin of the superorder Parasitiformes was placed later in the Carboniferous-Permian. Most family-level taxa within the Acariformes were dated to the Jurassic and Triassic. The ancient origin of Acariformes and the early diversification of major extant lineages linked to the soil are consistent with a pioneering role for mites in building the earliest terrestrial ecosystems.

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The ecological functioning of dryland ecosystems is closely related to the spatial pattern of the vegetation, which is typically structured in patches. Ground arthropods mediate key soil functions and ecological processes, yet little is known about the influence of dryland vegetation pattern on their abundance and diversity. Here, we investigate how patch size and cover, and distance between patches relate to the abundance and diversity of meso-and microarthropods in semi-arid steppes. We found that species richness and abundance of ground arthropods exponentially increase with vegetation cover, patch size, and patch closeness. The communities under vegetation patches mainly respond to patch size, while the communities in the bare-soil interpatches are mostly controlled by the average distance between patches, independently of the concurrent changes in vegetation cover. Large patches seem to play a critical role as reserve and source of ground arthropod diversity. Our results suggest that decreasing vegetation cover and/or changes in vegetation pattern towards small and over-dispersed vegetation patches can fast lead to a significant loss of ground arthropods diversity in drylands.

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The genus Anystipalpus Berlese, 1911, of uncertain prior placement in the superfamilies Ascoidea or Dermanyssoidea, is redescribed, based on reexamination of type and other material of the type-species, A. percicola Berlese, and of material representing Anystipalpus livshitsi (Eidelberg) new combination and two new species, A. labiduricola n. sp. and A. kazemii n. sp. Anystipalpus nataliae (Eidelberg) new combination and Anystipalpus ukrainicus (Sklyar) new combination are determined to be junior synonyms of A. percicola Berlese and A. livshitsi (Eidelberg), respectively, new synonymies. The genus is known thus far only from adult females phoretic under the elytra of carabid beetles and the tegmina of labidurid earwigs in Eurasia. The relationships between it and the closely related Antennoseius Berlese, 1916 and Vitzthumia Thor, 1930, are reviewed, and the options for the family level placement of these genera are reconsidered. Attention is given to some gnathosomatic attributes that are commonly overlooked in description of species of these closely related genera. Phoresy and the role of adult female morphs in the life history of these mites, as well as the extraordinary phoretic association of one species with earwigs are discussed.