Flora of North America species comparison

Of conservation concern.

Previous to its discovery in Iceland, as Grimmia grisea (H. C. Greven 1998), G. reflexidens was known from only the Southern Hemisphere. It had previously been collected east of East Bay, Newfoundland, now the only known locality in North America, but was not recognized as G. reflexidens. The latter is similar to G. asperitricha Dixon & Sainsbury of New Zealand, and the two species have been confused by G. O. K. Sainsbury (1945) as well as by R. Ochyra (1993). J. Muñoz (1998b) synonymized G. reflexidens with G. sessitana. However, the former is readily separated from the latter by: (1) enlarged perichaetial leaves, (2) decurrent awns, (3) non-bulging laminal cells, and (4) dioicous sexual condition. Capsules are unknown from Northern Hemisphere material, but G. reflexidens lacks stomata while they are present for G. sessitana. Although G. reflexidens and G. teretinervis both have decurrent awns they are easily separated by a number of characters: G. reflexidens grows in compact cushions, has long awns, and a semicircular costa; G. teretinervis grows in loose clumps, is hyaline-tipped to short-awned, and has a unique costa that is distally almost completely circular in transverse section.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In Canada, Grimmia unicolor is found predominantly around the Great Lakes of southern Ontario eastward into southwestern Quebec, with a disjunct site in Newfoundland. In the United States, it is also commonly found in the Great Lakes region and extending eastward into southwestern Maine. The disjunct sites in British Columbia and on the Seward Peninsula may be a Beringial link with populations in Asia, where this species is widely distributed, and in northern Europe. Grimmia unicolor is often found in the splash zone of rocky shorelines, especially cliffs, and along rivers. This habitat is rarely occupied by other species of the genus, except for G. olneyi. Grimmia unicolor is readily distinguished from other species in the subgenus by its leaf morphology. Its leaves are oblong-lanceolate to ligulate, with an obtuse, rounded apex which is muticous. Grimmia olneyi has an acute leaf apex with long awns, and its basal marginal cells are quadrate, contrasting with the rectangular cells of G. unicolor. Sporophytically, G. unicolor typically has a straight seta while that of G. olneyi is sigmoid. Grimmia unicolor has a much narrower costa proximally and lacks an awn, in marked contrast to the broad costa and robust awn of G. laevigata. The leaf shapes of these two species are distinct, with G. unicolor having a pronounced ovate base and narrow leaves tending towards being ligulate, while G. laevigata has broadly oblong-ovate leaves without a shoulder separating the distal and proximal lamina.

(Discussion copyrighted by Flora of North America; reprinted with permission.)