Taxonomic notes on some European species of Bryum (Bryopsida: Bryaceae)

Abstract The genus Bryum has more currently recognized species (ca 90) than any other moss genus in Europe and a reputation for taxonomic difficulty. It also includes numerous rare species, with 17 treated in the British Red Data Book. Despite large reductions over the past seventy years in the number of European taxa treated as species, several of the currently recognized species are known to intergrade, including some of those currently regarded as priorities for conservation. It is also apparent that there are several variable complexes within the genus in which plants with a few distinctive characters have traditionally been given species rank, yet few if any attempts have ever been made to ascertain how far different characters are correlated. From study of a variable population of B. inclinatum auct. it is demonstrated that numerous characters of the capsule (size of the capsule mouth, character of the exothecial cells, shape of the operculum, structural details of the exostome teeth) may be correlated because of causal interactions during growth and should not be regarded as independent characters. A combination of field and herbarium studies has been used to revise the taxonomy of some European Bryum species. The following taxonomic changes are proposed: B. archangelicum Bruch & Schimp. is conspecific with B. inclinatum (Brid.) Turton and should be used to replace this illegitimate name, instead of B. amblyodon Müll. Hal. or B. imbricatum (Schwägr.) Bruch & Schimp. ; B. curvatum Kaurin & Arnell is another synonym of this variable species. Synonyms of the variable B. arcticum (R. Br.) Bruch & Schimp. include B. bryoides (R. Br.) Wijk & Margad. , B. purpurascens (R. Br.) Bruch & Schimp. and B. lawersianum H. Philib. B. axel-blyttii Kaurin ex H. Philib. and B. acutiforme Limpr. are best treated as synonyms or infraspecific taxa of B. calophyllum R. Br. B. platyloma Schwägr. , B. rufifolium (Dixon) Demaret & R. Wilczek and B. validicostatum Cardot & Dixon are regarded as synonyms or varieties of B. capillare Hedw. B. barnesii Wood ex Schimp. and B. balticum Nyholm & Hedenäs should be treated as synonyms of B. dichotomum Hedw. , to which they are linked by many intermediate plants. B. stirtonii Schimp. is regarded as a synonym of B. elegans Nees, and B. nitidulum Lindb. as a synonym of B. intermedium (Brid.) Blandow. Bryum caespiticium var. imbricatum Bruch & Schimp. apparently merits species rank and should be known as B. kunzei Hoppe & Hornsch. Differences between B. kunzei and B. funckii Schwägr. are described, demonstrating that adoption of the latter name in the British Census Catalogue to replace B. caespiticium var. imbricatum was incorrect. Bryum moravicum Podp. is an earlier name that should replace B. laevifilum Syed. Synonyms of B. pallens Sw. include its var. fallax Jur. , B. oeneum Blytt ex Bruch & Schimp. , B. subelegans Kindb. and European plants assigned to B. rutilans auct. B. torquescens Bruch & Schimp. merits separation at species rank from B. capillare ; its synonyms include B. icodense H. Winter. B. mamillatum Lindb. and B. oelandicum H. Philib. are best regarded as synonyms of B. warneum (Röhl.) Brid. Several populations of B. knowltonii Barnes have much larger spores than are reported in the literature (up to 43.5 μm) and its exostome teeth sometimes have oblique cross-walls.