Brachythecium salebrosum: Some Like It Temperate

Brachythecium salebrosum, photographed in Slovakia by M. Lüth.

Brachythecium salebrosum is a species of moss found in many temperate regions of the world. It often grows in drier habitats than other mosses; in a study of the effects of human disturbance on forest moss communities in Estonia, B. salebrosum made up slightly less than a tenth of the moss flora in unmanaged forests, but accounted for more than a quarter of the flora in managed forests (Vellak & Paal 1999). Brachythecium salebrosum is known from Eurasia, North America, southernmost Africa and Australasia. Interestingly, it hasn't yet been recorded from South America (Delgadillo 1993), and an explanation for its distribution would need to explain how it came to disperse (or vicariate) between North America and South Africa yet bypass South America and northern Africa. Another oddity in its distribution can be seen in comparison to the similar species Brachythecium rotaeanum: while both species are found in Eurasia and North America, B. salebrosum is more common in the western part of each continent while B. rotaeanum dominates in the east (so as one travels east from Europe, the distribution bands are salebrosum-rotaeanum-salebrosum-rotaeanum) (Ignatov et al. 2008). Some authors (particularly European ones) have expressed scepticism about the distinction between these two species, but they are distinguished by both morphological and molecular characters according to Ignatov et al. (2008).

Individual leaf of Brachythecium salebrosum, photographed by Russ Kleinman & Karen Blisard.

Distinguishing Brachythecium salebrosum from related species is, admittedly, not a simple task. Specimens of this species can vary quite significantly across their range. Generally, however, B. salebrosum has plicate leaves (i.e. they are folded longitudinally like an accordion) that are more or less falcate in shape with serrated margins. There is a clearly distinct group of small subquadrate cells at the lower corners of the leaf. The spore capsules are held more or less horizontally, and the seta supporting the capsule is generally about two centimetres high (Ignatov et al. 2008).

REFERENCES

Delgadillo M., C. 1993. The Neotropical-African moss disjunction. The Bryologist 96 (4): 604-615.

Ignatov, M. S., I. A. Milyutina & V. K. Bobrova. 2008. Problematic groups of Brachythecium and Eurhynchiastrum (Brachytheciaceae, Bryophyta) and taxonomic solutions suggested by nrITS sequences. Arctoa 17: 113-138.

Vellak, K., & J. Paal. 1999. Diversity of bryophyte vegetation in some forest types in Estonia: a comparison of old unmanaged and managed forests. Biodiversity and Conservation 8: 1595-1620.