Free-living mites (Acari) of the Franz Josef Land Archipelago, the coldest Old World territory: diversity, geographic distributions, assemblages

Abstract

Studies on the mites from the Franz Josef Land Archipelago have become strongly belated and impeded because of the archipelago’s highly remote location (1,500 km from the mainland) and logistics barriers. Material collected during five expeditions (1981−2016) has revealed a total of 48 species of free-leaving mites, yet two species are added based on literature data (absent in the present material). Altogether, 17 families, 22 genera, and 23 species are reported for the first time to inhabit the archipelago. The presence of 16 from 26 previously recorded species must be confirmed. Like in the other parts of the polar desert zone, arachnids (52 species, including two spider species found in previous works) generally appear to be more diverse than insects (14 species, found in previous and present works), this being a unique feature of that natural zone. Prostigmatic mites (19 species) are twice as diverse as oribatid mites (10 species). The mesostigmatic mite genus Arctoseius Thor, 1930 is the most species-rich (8 species of all 13 mesostigmatic mite species collected), as previously reported throughout the Arctic. The acarofauna is strongly fragmentary, 23 of all 30 genera (76.7%) being represented by one species each. The fauna of Mesostigmata is much more specialized (in terms of cryophily) in comparison to Oribatida, true arctic and arctic-montane species amounting to 92% versus 10%, respectively. The total mite abundance varies between 120 and 3,760 ind./dm2, being the maximal in a tundra-like habitat on a south-faced slope in Tikhaya Bay, Hooker Island. Small and thin-tegumented members of Eupodidae, Tydeidae and Nanorchestidae, all using liquid food alone, predominate everywhere across the archipelago as they do throughout the polar deserts of both Hemispheres. Small oribatids (Liochthonius spp., Brachychthoniidae) are often also abundant. All these taxa represent the most ancient lineages of the superorder Acariformes known to date back to the early or middle Devonian. The rather large and well-sclerotized members of the oribatid family Ceratozetidae are abundant only in the best heated habitats with an extended vegetation season.