A review of gamasid mites (Parasitiformes,Mesostigmata) dwelling in the taiga of the Pechoro-Ilychskii Nature Reserve (northern Cis-Ural Region) with analysis of their assemblages in spruce forests

In the plain taiga of the Pechoro-Ilychskii Nature Reserve, 91 species of gamasid mites have been revealed. Cheiroseius (7 species), Veigaia (6), Arctoseius (5), Dendrolaelaps (5), and Dinychus (4) are the most diverse genera. European (29%), Palaearctic (27%), and Holarctic species (30%) are represented in the fauna by somewhat equal fractions, whereas cosmopolitan and semicosmopolitan species constitute about 14%. Comparison of gamasid assemblages populating certain habitats allowed revealing two distinct groupings, namely, forest and floodplain ones. Forest assemblages are characterized by high population density (220–760 ind./dm²) and by predominance of Parazercon radiatus, Zercon forsslundi, Veigaia nemorensis, Gamasellus montanus, and Trachytes spp. Floodplain assemblages are less abundant (80–130 ind./dm²) and comprise mainly meadow and hydrophilic species (A. cetratus, Cheiroseius spp. Gaeolaelaps spp., and Gamasellodes bicolor). Low diversity of the family Parasitidae (4 species) and structural peculiarities of assemblages dwelling in coniferous forests (namely, the absence of Pergamasinae and significant fractions of Veigaia, Gamesellus, Trachytes, and also of representatives of the family Zerconidae) demonstrate similarities between the mesostigmatan population of this northern European region and that of the Siberian taiga. Solitary records of such Arctic species as Arctoseius ornatus and Zerconopsis labradorensis, and of the hypoarcto-montane species Iphidinychus gaieri within the taiga belt, seem to reflect the instability of range margin. Taking into account the literary data, we recognize a complex of boreal and borealmountain species (Trachytes edleri, Dinychus septentrionalis. D. crassus, Caurozercon duplex, Neozercon smirnovi, Zercon forsslundi, and Z. zelawaiensis) in the Palaearctic fauna. Their habitats, however, are not restricted only to dark coniferous forest along. The structure of gamasid mite assemblages in mesophytic spruce forests of the Palaearctic varies strongly. By contrast to vascular plants, where many species accompany the dark coniferous taiga everywhere, there is not a single mesostigmatic mite species common to all the spruce forests analyzed, ranging from Romania in the west to Sakhalin Island in the east. On the whole, changes in gamasid mite assemblages across the spruce forest belt seem to follow a succession of meridional changes in gamasid faunas regardless of an edificatory spruce species.