Unstable microhabitats (merocenoses)—such as decayed wood, ant hills, bird and mammal nests—constitute an important component of forest (and non-forest) environments. These microhabitats are often inhabited by specific communities of invertebrates and their presence increases the total biodiversity. The primary objective of the present study was to compare communities of Uropodina (Acari: Mesostigmata) inhabiting soil and unstable microhabitats in order to explore the specificity of these communities and their importance in such ecosystems. Uropodine communities inhabiting merocenoses are often predominated by one or two species, which constitute more than 50 % of the entire community. Many species occur commonly in particular merocenoses, but are absent or rare in soil and litter, for example, Allodinychus flagelliger, Metagynella carpatica, Oplitis alophora, and Phaulodiaspis borealis. The biology of Uropodina inhabiting unstable microhabitats is modified by the adaptations required for living in such habitats. Mites associated with merocenoses developed special dispersal mechanisms, such as phoresy, which enable them to migrate from disappearing environments. Communities of Uropodina in soil and litter predominately consisted of species which reproduce parthenogenetically (thelytoky), whereas in merocenoses bisexual species prevail.

This article presents a Red List of mite species from the suborder Uropodina (Acari: Parasitiformes) occurring in Poland. Evaluation of the conservation status of the analyzed species was compiled on the basis of new criteria, which may also be applied to other groups of soil fauna. The authors employ the names of categories proposed by the International Union for Conservation of Nature (IUCN). One of our aims was to review the IUCN criteria to ascertain whether they are applicable in an attempt to assess the danger of extinction of soil invertebrates, and to see whether the criteria can be adapted to make such an assessment. The analyzed material contained 93 mite species obtained from 16,921 soil samples, which were collected between 1961 and 2017 in the whole area of Poland. The categories were assigned to species on the basis of the frequency of the species, but also other factors were taken into account, such as microhabitat specificity, vulnerability to detrimental conditions, and shrinking of local populations. One of the analyzed species can now be regarded as extinct, over 25% of the species (26 spp.) were labeled as critically endangered, and most of them (33 spp.) were categorized as vulnerable—the other species were assigned to the categories endangered (13 spp.), near threatened (10 spp.), and least concern (10 spp.).

Bird and mammal nests provide microhabitats that support a range of other species, including invertebrates. However, the variation between communities of nest-dwelling invertebrates in different nests is poorly understood. The major aim of this study was to analyze the assemblage structure of mites from the suborder Uropodina (Acari: Mesostigmata) and from superfamily Crotonioidea (Acari: Oribatida) inhabiting nests of the wood warbler, Phylloscopus sibilatrix (Aves: Passeriformes), located on a forest floor in Białowieża Forest, in eastern Poland. We also assessed the correlation between the nest material used by the birds with the assemblage structure of Uropodina mites, and compared the results with published studies of the nests of other birds and a mammal (common mole, Talpa europaea), and also with communities of mites inhabiting the soil. The field research was conducted in the strict nature reserve of the Białowieża National Park, a near-primeval European temperate forest. In 2019, immediately after the breeding period, 69 wood warbler nests and 439 soil samples were collected. Analyses revealed assemblages of Uropodina mites inhabiting the nests that consisted of 14 species, mostly common soil species. Only five species of oribatid mites from superfamily Crotonioidea were present in the nest material. Analyzed nests had a high percentage of tree leaves and grass blades, whereas moss was the least frequent component of the nest material. The Uropodina mites were more abundant in the nests that had greater amounts of grass blades, but similar relationships were insignificant for the nests with varying amounts of tree leaves or moss. The assemblages of Uropodina mites inhabiting wood warbler nests were very similar to those found in soil and nests of the common mole, but they lacked typical nest-dwelling species of Uropodina (i.e., specialized nidicoles).

We examined the species composition and community structure of mites of the order Mesostigmata (Acari) in nests of the Eurasian griffon vulture (Gyps fulvus Hablizl, 1783) in Croatia. Material collected from 18 nests included 565 mites belonging to seven species. The most abundant species were Leiodinychus orbicularis (C.L. Koch, 1839) (Trematuridae) and Androlaelaps casalis (Berlese, 1887) (Laelapidae). The results were compared with the community structure and frequency of dominant species of Mesostigmata in nests of 32 other bird species. Leiodinychus orbicularis occurred in the nests of 13 species of birds. It is a typical nidicolous species which occurs most frequently in the perennial nests of birds of prey. In contrast, A. casalis rarely occurs in the nests of birds of prey.

The current study concerns phoresy in uropodid mites on centipedes. Research was conducted for eight months (April–November 2006) in three habitat types, each exposed to different degrees of anthropogenic impact. The centipedes were collected monthly from all accessible microhabitats across the areas studied. We collected a total of 733 lithobiomorph centipedes representing three species. We found 43.8% of these individuals transported a total of 3376 specimens representing one Uropodina superfamily, i.e. phoretic deutonymphs of Oodinychus ovalis (CL Koch, 1839) (18%) and Uroobovella pulchella (Berlese, 1904) (82%). Mites were found on nearly all (99%) studied individuals of Lithobius forficatus (Linnaeus, 1758). The number of deutonymphs on one centipede varied from 1 to 273 specimens. The dynamics of phoresy was different for both uropodid species and each of the studied areas. The two most important factors affecting phoresy of mites on centipedes were the type of a tree stand (presence of particular tree species and probably also afforestation density), and deadwood availability. The degree of anthropogenic impact seems to influence the intensity of carrier infestation. We observed that most of the phoretic deutonymphs were attached to the anterior and middle segments of the carrier’s body.