Oribatid mite diversity in Rhododendron ponticum L. canopy along an altitudinal gradient in Mtirala National Park

Oribatid mite diversity along an altitudinal gradient from 10 m to 850 m a.s.l. was investigated on the twigs and leaves of Rhododendron ponticum L. in Mtirala National Park. Forest floor sampling (mineral soil and litter) was also performed in the same locations. Altogether, 77 species of oribatid mites were identified. 31 species were found in the canopy and 64 species were found in the mineral soil and litter. Juveniles made-up 7.6% of the canopy fauna. Ommatocepheus ocellatus (Michael, 1882), was a new finding for Mtirala National Park. Steganacarus (Tropacarus) patruelis Niedbala, 1983 was the most numerous species found on twigs and leaves. Almost the whole canopy fauna (94%) belonged to higher oribatids (Brachypilina) and the lower oribatids were only represented by only S. patruelis and Camisia segnis (Herman, 1804). Canopy fauna was separated from those found on the ground supporting the importance of both habitats in maintaining overall biodiversity. The highest number of individuals and the highest number of species was found on mid-altitudes, decreasing with increasing elevation. There was no difference in species richness between twig and leaf habitats, whereas abundance was much higher on twigs. We showed that rhododendron understory harbored well established and abundant oribatid fauna preserving rare and unique species that enhance regional biodiversity.