Notes on Brachymenium in Guyana with a new species from Mt. Ayanganna

Abstract A relative of the African species described by Brotherus as Bryumperspinidens, has been discovered in Guyana with erect capsules and a short inner peristome. The Guyana material is recognized as a new species, and both species are placed in the genus Brachymenium. The characteristics that distinquish the genus are discussed with reference to the Guyana specimens of Brachymeniumspeciosum.


Introduction
Study of bryophyte collections obtained during the Smithsonian Biological Diversity of the Guianas project, has revealed a number of interesting species. Among these are two two collections of a bryaceous moss with capsules identifiable as a Brachymenium Schwaegr., Spec. Musc. Suppl. 2(1): 131. 1824, with a leaf that superficially matches the illustration of Bryum perspinidens Broth. in the Brotherus treatments in the two editions (1904 and 1925) of Engler and Prantl. The only problems were that the Brotherus illustration was of an African species named as a Bryum. The spiniform teeth of the leaf margins were nevertheless similar, and a relationship seemed to be involved. As for the generic placement, the Brotherus (1897) species was described from sterile material so that the placement in Bryum Hedw. lacked any real evidence.
The relationship of Guyana Highland species to African species fits a pattern noted by Robinson (1965). In addition, there is ample material from Guyana of another species of Brachymenium, B. speciosum that is newly discussed and illustrated.

Methods
Specimens in this study were obtained during the Smithsonian Biological Diversity of the Guianas Program conducted over a period of years from 1985 to 2014 (Kelloff et al. 2019). The particular specimens of the new species involved in this study were collected during a separately funded trip conducted by M.D. Clark in 2001 that collected on Mt. Ayanganna. The bryophytes were deposited at the US National Herbarium awaiting identification. They have been in storage since that time.
A note with the specimens indicates that when they arrived in the US they were irradiated during the Anthrax scare of 2001.

Results
The South American material includes one species that seems to be distinct from others from the Western Hemisphere (see for example Allen 2002) and from the related African species.  Description. Stems up to 3 cm tall, leaves not closely spaced, rather firm in structure but contorted when dry and resistant to wetting. Costa percurrent into a long slender acumination, median cells narrowly oval, with firm walls showing slight porosity, mostly 80-100 μm long and ca. 30 μm wide, without shorter quadrate cells at base, margin with numerous rows of linear pale cells forming a strong border, border with numerous cells projecting as spiniform teeth, such spiniform teeth extending onto apical acumination. Synoicous? Seta pale yellowish-red, ca. 17 mm long, smooth. Capsules erect, ca. 2 mm long, with short hypophysis, operculum short-rostrate, higher than wide. Outer peristome teeth reddish, rudimentary, ca. 80 μm long, inner peristome a low pale membrane ca. 70 μm without projecting segments or cilia. Calyptra not seen. Spores ca. 10 μm in size.  The peristome teeth of the new species have proven extremely fragile, possibly because of the radiation treatment.
The spiniform teeth of the leaf margin are distinctive, but the manner in which they occur on the acuminate apical extension is reminiscent of the illustration by Brotherus (1904: 557 fig. C;1925: 367, figs C, D). This illustration has led to the comparison, but it proves to be somewhat inaccurate compared to the more recent illustration made from the type by Ochi (1972) The African species is well illustrated by Ochi (1972), but the type from Helsinki has been borrowed not because of doubts of relationship so much as to insure that the two species are not the same. The principle difference is the absence of spinose teeth extending on to the apical acumination of the leaf. Nevertheless, there is no doubt the two are close, and the African species was placed in Bryum only because there was no sporophyte to indicate otherwise. A important point derived from the Ochi study is that none of the species in typical Bryum have spinose marginal teeth, all with such teeth are in what is now in the Brachymenium, Rhodobryum relationship. On the basis of the evident relationship between the African and Guyana species, the following transfer of the African species is provided. Figure 1D Bryum perspinidens Broth., Bot. Jahrb. Syst. 24: 246. 1897. Britische Ostafrika, Seengebiet: Ru-Nssóro, 3300-3600 m (Uganda: Ruwenzori, heather forest 10-12000'), Scott Elliot 266, Sterile. Rhodobryum perspinidens (Broth.) Pócs, in Bizot & Pócs, Acta Bot. Acad. Sci. Hungaricae 25: 257. 1979 [1980]. With record of species from Tanzania, also sterile. Ochi (1972) indicated the species was rather an oddity in Bryum Hedw. subgenus Rhodobryum Schimp. in which he placed it.

Notes. Placement of the new species in
Brachymenium is based on the capsules being erect with an inner peristome being a low membrane lacking segments or cilia, the traditional distinctions of the genus. Recent DNA studies (Pedersen et al. 2003, Pedersen andHedenas 2005;Cox and Hedderson 2003) (Robinson 1965;Ochyra et al. 2018). A survey of the illustrations in Brotherus (1904Brotherus ( , 1925 shows an additional trend in Brachymenium that is lacking in typical Bryum, conical to rostrate opercula such is seen in the new species. In fact, within the present definition of Brachymenium, fully rostrate opercula occur in another species recently collected in Guyana. Brachymenium speciosum (Hook. & Wils.) Steere. Figure 2 Notes. The latter species has been collected on a mountain near Ayanganna as indicated below. Mt. Wokomung, Little Ayanganna, upper slopes of highest point of Mount Wokomunga massif. 5°5'8"N, 59°50'32"W. elev. 1525 m. Tepui scrub forest on sandstone showing elongate exostome teeth erect on one half and reflexed on other half, the latter showing endostome lacking cilia and segments. The photographs were taken using a Leica DM4B Compound microscope, 5× objective.