Underground diversity: Uropodina mites (Acari: Mesostigmata) from European badger (Meles meles) nests.

Badgers can gather huge quantities of organic material to build their nests for winter time and to rear their cubs. Moreover, badger burrows (setts) are characterized by specific microclimate with quite stable temperature and humidity. Their fauna is poorly studied, especially in respect of saprobiontic Uropodina mites. In 2018-2019, we monitored 94 badger setts to search for nest material that had been thrown away during cleaning of the chambers after mating and winter sleep. In the collected material from 32 badger nests, we found 413 Uropodina mites of 16 species, in various stages of development (adults, protonymphs, and deutonymphs). The community was dominated by three mite species: Trematura patavina (22.5%, n = 93), Oodinychus ovalis (17.2%, n = 71), and Olodiscus minima (15.5%, n = 64). Other nidicolous-i.e., nest-dwelling-species included: Nenteria oudemansi (14.8%, n = 61), Phaulodiaspis borealis (7.0%, n = 29), Phaulodiaspis rackei (4.6%, n = 19), Uroseius hunzikeri (1.7%, n = 7), Uropoda orbicularis (1.5%, n = 6), and Apionoseius infirmus (1.0%, n = 4). The most frequent species were: Oodinychus ovalis (62.5%, 20 nests), N. oudemansi (46.9%, 15 nests), and Olodiscus minima (40.6%, 13 nests). Detrended correspondence analysis indicated that the Uropodina community from badger nests differed from that of mole nests, studied earlier. In setts, the Uropodina community included T. patavina and N. oudemansi, which were for the first time recorded from underground badger nests. This is the first record of N. oudemansi from Poland.