Species composition and abundance of the oribatid fauna (Acari, Oribatida) at two lakes in the Fløyen area, Bergen, Norway

Abstract

Species composition and abundance of the oribatid fauna (Acari, Oribatida) at two lakes in the Fløyen area, Bergen, Norway Oribatid communities from the edges of two lakes in the Fløyen area, Bergen, Norway, were compared in June 2005. The lower lake, Blåmansvannet (412 m a.s.l.), is surrounded by spruce forest, while the ‘Higher Lake’ (513 m a.s.l.), is above the tree line. Both lakes have a low pH and their edges are dominated by Sphagnum mosses. The abundance of total mites, as well as of Oribatida, were almost 2-fold higher at the ‘Higher Lake’ (51 510 and 51 160 ind./m2, respectively), while species diversity was lower than at Blåmansvannet. On the shore of Blåmansvannet, the eudominant (20% < D ≤ 40%) species was Trimalaconothrus maior, while Liochthonius peduncularis, Limnozetes ciliatus, and Nanhermannia cf. coronata were dominant (10%< D ≤ 20%). At ‘Higher Lake’, the eudominant species was Limnozetes ciliatus, which reached a 4-fold higher abundance (15 930 ind./m2) than at Blåmansvannet, and dominant species were Liochthonius alpestris, Nanhermannia cf. coronata, and Platynothrus punctatus. At both lakes, juveniles made up about 30% of all oribatids. Four species are new to Norway: Ceratoppia sexpilosa, Liochthonius alpestris, Liochthonius peduncularis, and Trhypochthoniellus longisetus.