Flora of North America species comparison

Grimmia ovalis is common and widespread in high elevation sites in western North America from southern British Columbia along the Rocky Mountain corridor to southern New Mexico and south central California. H. A. Crum and L. E. Anderson (1981) rejected all reports of G. ovalis from eastern North America. However, we have seen specimens from that area, although scattered and rare. It is not surprising that the species occurs in the eastern part of the continent given that it is widespread across the Laurasian continental plates and in India. Outlier sites in the Yukon and southern Greenland connect the North American populations to those in Asia and Europe, respectively. In western North America, G. ovalis is most often confused with G. longirostris and G. laevigata. While superficially similar to G. longirostris, G. ovalis has concave leaves with plane margins and is dioicous, while G. longirostris has keeled leaves with a recurved margin and is autoicous. Other points of separation are discussed under G. longirostris. Typical specimens of G. ovalis are readily separated from G. laevigata by their ovate-lanceolate leaves with a well-defined ovate base and narrowly attached awns. However, both of these species are variable in leaf shape, and while the awn of G. ovalis is usually narrowly attached, sometimes it is quite broad and may border on being decurrent. These specimens can be identified by the width of the costa and the basal areolation. Grimmia ovalis has a costa that is narrow at the base, while G. laevigata has a distinctly broad costa covering up to 1/3 of the base. The basal marginal cells of G. ovalis are most often short- to long-rectangular and hyaline while those of G. laevigata are always oblate to quadrate and not hyaline. In eastern North America, specimens of G. ovalis have been misidentified as G. olneyi. Aside from seta and capsule differences, G. ovalis has rectangular basal marginal laminal cells and its basal juxtacostal cells are long-rectangular to elongate; see also under G. olneyi.

Based on identifications by Greven, W. A. Weber et al. (2003) reported Grimmia bernoullii in the United States. That species differs from G. ovalis by its more ovate leaves without shoulders and with plane margins, costa broad at the base and disappearing in mid leaf, and sporophytically by its ellipsoid capsule with long-rostrate, straight operculum, and mitrate calyptra. Hastings has examined duplicate specimens from Missouri of those cited by Weber et al. and has determined that they do not deviate significantly from G. ovalis, having rather narrow leaves, costa narrow at the base and remaining strong in mid leaf, and with many leaves having incurved margins. The specimens were sterile and therefore sporophytic characters could not be determined. Based on these observations Hastings excludes G. bernoullii from the North American flora, although Greven would still retain the species.

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

Grimmia longirostris is one of the most common species of the genus. It is most common in the eastern ranges of the Rocky Mountains, ranging from western Texas through the Canadian Rockies, and throughout much of Alaska. It is widely distributed in the Canadian sub-Arctic and Arctic, and is known from Greenland. With the exception of disjunct sites in Oklahoma and North Carolina, it is absent in the American Great Plains and Southeast. These latter areas are largely composed of calcareous rocks, a substrate avoided by G. longirostris. It is rare in coastal areas, becoming more common inland.

As Grimmia affinis, G. longirostris has commonly been placed as a subspecies of G. ovalis. Despite G. Sayre’s (1951) resolution of the differences between these taxa, a large proportion of specimens in major herbaria in North America that are named G. ovalis are actually G. longirostris. However, G. ovalis is dioicous and has leaves with plane margins that are broadly concave distally, usually with a distinct ovate base and well-defined shoulders. In contrast, G. longirostris is autoicous, and has leaves with one recurved margin, that are narrowly keeled distally, with a poorly defined basal region, often without a distinct shoulder. These characters clearly separate these two taxa at the specific level. Hastings puts G. longirostris into a group that also includes G. arizonae and G. pilifera. Grimmia longirostris is separated from those two species by non-sheathing leaf bases, usually long-exserted capsules, and cladautiocous sexuality. Grimmia longirostris is further separated from G. pilifera by having a stem with a distinct central strand and a thin epidermis, a costal transverse section that is typically reniform, and leaves that are recurved on only one margin. Rare specimens of G. longirostris with immersed capsules in the American Southwest may be almost indistinguishable from G. arizonae. In extremely xeric environments, specimens become friable and break into individual strands, making determination of the cladautiocous sexuality impossible. In these circumstances identification will always be uncertain. However, the leaves of G. longirostris are not sheathing; they are only loosely attached to the stem and usually can be peeled off intact. In contrast, the leaves of G. arizonae are sheathing and strongly attached to the stem; they often break at the base when trying to remove them. The costal transverse sections of G. longirostris are characteristically reniform (J. Muñoz 1998) while those of G. arizonae are usually semicircular. However, gradations from semicircular to reniform are not uncommon.

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