Lepraria jackii Tønsberg
Nomenclatural data
Sommerfeltia 14: 200 (1992)
Leprose, diffuse, powdery, often cottony, soft, often thick; light green to light grey; irregularly shaped; thallus margin diffuse; medulla often evident, white; soredia loosely packed, mostly small, sometimes up to 60 µm in diam., with short to medium projecting hyphae usually present.
L. jackii contains atranorin and one or two fatty acids – jackinic/rangiformic and roccellic/angardianic acid. All Greenland specimens contained atranorin, fatty acids were encountered as follows: (1) roccellic/angardianic acid only (n=9); (2) jackinic/rangiformic acid only (n=7); (3) jackinic/rangiformic and roccellic/angardianic acid (n=2); (4) unidentified fatty acid (n=2).
L. jackii is chemically similar to L. borealis, but differs clearly from it morphologically; the latter belongs to the L. neglecta group and is characterized by coarsely granular and hard soredia. A few specimens from Greenland have abnormally large and densely packed soredia.
Recently Lepraria toensbergiana Š.Slavíková & Kukwa was separated from the morphologically identical L. jackii on the basis of its chemistry (atranorin together with the newly described fatty acid toensbergianic acid) and its montane distribution (Bayerová et al. 2005, Bayerová & Haas 2005). However, Baruffo et al. (2006) found toensbergianic acid as an accessory only in the specimens containing other fatty acids that were considered typical to L. jackii. They also observed a wide ecological and distributional overlap between these species. Furthermore, the ITS sequences of the species differ only in four nucleotides (Bayerová et al. 2005). As no other evidence for the distinctiveness of the species was available, L. toensbergiana was reduced to a synonym of L. jackii (Baruffo et al. 2006). From Greenland no specimens containing toensbergianic acid are known.
Three further species related to L. jackii were described by Slavíková-Bayerová & Orange (2006), Lepraria celata Š.Slavíková, L. humida Š.Slavíková & Orange, and L. sylvicola Orange, chemical separation of which is based on the contents of atranorin and different fatty acids. In this paper we still treat L. jackii s. lato.
Ecology and distribution

On mosses and soil, sometimes overgrowing other lichens.
Reported here as new to Greenland. L. jackii is mainly found in the Low Arctic, with only 2 localities on the east coast in the High Arctic zone.
Saag, L., Hansen, E. S., Saag, A. & Randlane, T. 2007.