Disentangling Scandinavian species hidden within Meesia uliginosa Hedw. s.l. (Bryophyta, Meesiaceae)

The molecular variation (atpB–rbcL spacer, rpl16 G2 intron, trnGUCC G2 intron) among 50 Scandinavian specimens of Meesia uliginosa s.l. was analysed in the context of three other Meesia species, with Paludella squarrosa as outgroup. The molecular variation within M. uliginosa correlates with morphology, and shows that three species exist: M. uliginosa Hedw., M. minor Brid. and M. minutissima Hedenas sp. nov. Whereas M. uliginosa s.str. is widespread, in Scandinavia the other two species are restricted to the mountains. The three species differ in quantitative features, such as, plant size, leaf size, costa width, leaf apex shape, seta length and spore capsule size. Because the species overlap in several of these features, a combination of seta length and the ornamentation of the exostome outside are the safest characters for identification. Leaf apex shape, small spore capsules in M. minutissima and large spores in M. minor serve as additional identification help. Meesia minutissima is presently only known from Scandinavia. The other two species are more widespread, although further investigations are required to find out their exact distributions.