Vertical Distribution of Mites (Acari) in a “Miniature Forest” of Sphagnum Mosses in a Forest Bog in Western Norway

Abstract

The Sphagnum habitat is a ”miniature forest” to the mites, of which the layers offer different microenvironmental conditions. We studied the vertical distribution of the Oribatida, Mesostigmata, and Prostigmata groups in four layers (0–5 cm, 5–10 cm, 10–15 cm, and 15–20 cm) of a forest bog on Neshalvøya, Norway, to improve the knowledge of the ecology of these mites. The sampled bog was grazed by farm animals; thus, another aim was to investigate the vertical distribution of the oribatid species, which are intermediate hosts of tapeworms. The selected study site is known for its valuable yet increasingly endangered nature, so our aim was also to contribute to the knowledge on its diversity. We collected Sphagnum samples in four replicates and extracted them in the laboratory in modified Berlese funnels. In total, 16.880 mites were studied, including 16.384 Oribatida, 466 Mesostigmata, and 30 Prostigmata. The total abundance of mites, the Oribatida and Mesostigmata groups, was the highest in the upper layer of Sphagnum and decreased with depth, while the abundance of the Prostigmata did not follow any pattern. Among the Oribatida, at deeper layers, significant declines in abundance were observed in adults, but not in juveniles. Most oribatid species, e.g., Nothrus pratensis, preferred the upper layer of Sphagnum, whereas some preferred deeper layers. For example, Suctobelbella acutidens and Carabodes femoralis preferred the 5–10 cm layer, Quadroppia maritalis the 10–15 cm layer, and Ceratozetes gracilis and Eulohmannia ribagai preferred the deepest layer of Sphagnum. Adults and juveniles of the same species showed a preference for the same layer. In total, 62 species of the Oribatida were recorded, including 11 species that are known to be intermediate hosts of tapeworms. Most of them occurred in the upper layer of Sphagnum. Over 20% of the species were found exclusively in deeper layers, so sampling these layers is important for a better evaluation of the mites’ diversity. Studying the vertical distribution of the mites in bogs helps us to understand their ecology, including their role as intermediate hosts of tapeworms, as well as their diversity.