Diverse Sphagnum Mosses Support Rich Moss Mite Communities (Acari, Oribatida) in Mires of Western Norway

A study of oribatid mites was carried out in six mires located in western, oceanic parts of Norway. Twenty Sphagnum species of five subgenera were collected from microhabitats representing trophic state and wetness gradients. In total, over 60,000 mites were extracted, including 58,000 Oribatida, representing 95 species (i.e. 30% of total species diversity of Oribatida in Norway). This is the highest number ever reported from mires, including 18 species new to Norway. The average density of the Oribatida was 54,126 ind./m 2 , but it differed among Sphagnum subgenera, being four times lower in the subgenus Rigida than in the other subgenera. Juveniles contributed nearly 40% of oribatids, in some species highly dominating in the age structure (up to 80% in Nothrus spp.), and two oribatid species were represented only by juveniles, so their inclusion is important in ecological studies. In some species the proportion of juveniles varied between the studied microhabitats. Localities, Sphagnum subgenera, and wetness gradient affected significantly the oribatid communities, so these factors should be taken into consideration in studies of the Oribatida in mires.