Nova Hedwigia 88 3—4 549—555 Stuttgart, May 2009 Sagediopsis pertusariicola (Verrucariales), a new lichenicolous ascomycete from the Arctic by Mikhail Zhurbenko Komarov Botanical Institute, Professor Popov 2, St. Petersburg, 197376, Russia With 8 figures and 1 table Zhurbenko, M. (2009): Sagediopsis pertusariicola (Verrucariales), a new lichenicolous ascomycete from the Arctic. - Nova Hedwigia 88: 549–555. Abstract: Sagediopsis pertusariicola dwelling on Pertusaria is described from the Russian Arctic. A revised description of Sagediopsis campsteriana is also provided; the species is confined to Ochrolechia. O. inaequatula is reported as a new host for the latter species. Introduction Sagediopsis (Sacc.) Vain. (Adelococcaceae Triebel, Verrucariales Mattick ex D.Hawksw. & O.E.Erikss.) is an exclusively lichenicolous fungal genus, which formerly comprised seven species (Index Fungorum 2008, LIAS names 2008). A specimen of Sagediopsis found on Pertusaria was first identified as Sagediopsis campsteriana (Linds.) D.Hawksw. & R.Sant. (Zhurbenko & Santesson 1996), a common fungus dwelling on species of Ochrolechia. However, examination of additional collections of Sagediopsis on Pertusaria has shown that they represent a distinct species, which is described here as new. A revised description of Sagediopsis campsteriana is also provided due to some discrepancies with literature data. Material and methods The material was examined by standard microscopic techniques using LOMO microscopes MBS-1, Mikromed-2 and Zeiss microscope Axio Imager A1 equipped with Nomarski differential interference contrast optics. Photographs were taken by Nikon Coolpix 5000 and AxioCamMR5 cameras. Microscopical measurements were made in water. Colour reactions of the exciple were examined in 10% KOH (K), those of the hymenium and asci in 1% Lugol’s iodine solution, directly (I) and after E-mail: [email protected] DOI: 10.1127/0029-5035/2009/0088-0549 0029-5035/09/0088-0549 $ 1.75 © 2009 J. Cramer in der Gebrüder Borntraeger Verlagsbuchhandlung, D-14129 Berlin · D-70176 Stuttgart 549.