A Key to the family Rhizogoniaceae in Africa

Extract from: O'Shea, B.J. 1997. British Bryological Society Expedition to Mulanje Mountain, Malawi. 9. Regmatodontaceae, Rhachitheciaceae, Rhacocarpaceae and Rhizogoniaceae (Bryopsida). Journal of Bryology 19(4).

This is a tropical/austral family with eight genera (see Koponen, Touw & Norris, 1986), only two of which (Leptotheca and Pyrrhobryum) are known from Africa. The other genera are mainly Asiatic, but some are also neotropical (Koponen et al, 1986; Manuel, 1980, 1981). This is a small family, recognised (Crum, 1994) by a gametophytic similarity to the Bartramiaceae and a sporophytic resemblance to the Mniaceae. The plants are acrocarpous in appearance, but the setae originate laterally or basally (capsules are common in African Pyrrhobryum, but unknown in African Leptotheca). The leaf cells are rounded and thick walled, and the leaf margins are toothed.

Key to African genera of Rhizogoniaceae

Leptotheca gaudichaudii Schwaegr. (originally located in the Aulacomniaceae and with a similar appearance to members of Aulacomnium) is known in Africa only from South Africa (Cape), and otherwise from South America, Australia and New Zealand (Churchill & Buck, 1982). In the Cape it is restricted to rock recesses and crevices in the mountain fynbos (Magill, 1987), but elsewhere is a common rainforest epiphyte, also growing on logs and rocks.

Pyrrhobryum Mitt.

The genus was revived by Manuel (1980) from Brotherus' Rhizogonium subg. Pyrrhobryum (Brotherus, 1925). The genus is separated from Rhizogonium by the possession of a multi-stratose border with all cells similar to those of the median lamina and with double teeth (Rhizogonium has the border mostly unistratose with some of its cells elongate and with single teeth) (Koponen et al., 1986). There are 11 species and 12 varieties described, by far the most frequent species being P. spiniforme, which is a variable and widespread pantropical species.

Three species and three varieties are recorded for Africa. Pyrrhobryum mauritianum (Besch.) Manuel is recorded from Réunion and Mauritius, and differs from P. spiniforme by its dioecious inflorescence, its robustness and its short leaves (Bescherelle, 1880). However, the type of this taxon in BM is annotated by C.C. Townsend: "I have examined inflorescences from the ... type ... and found them synoecious !....I cannot separate this specimen at any rate from R. spiniforme." I have thus excluded this taxon from the key as doubtfully distinct from P. spiniforme. The three varieties of P. spiniforme (var. brevifolium Besch., var. comorense C.Müll. and var. acunhense Besch.) also seem to be not worth distinguishing, representing points in a cline of variation. This just leaves two species to be separated.

Key to African species of Pyrrhobryum (after Magill, 1987)

Pyrrhobryum vallis-gratiae (Hampe) Manuel is endemic to the South African Cape (see Magill, 1987 for description and illustration); P. spiniforme is found in upland forest throughout Africa (see Koponen, Touw & Norris (1986), Magill (1987), Crum (1994) and Eddy (1996) for descriptions and illustrations. The latter taxon could be mistaken at first glance for a species of Mnium, but the vary narrow leaves, crisped when dry, give a very distinctive appearance.

References
Bescherelle E. 1880. Florule bryologique de la Réunion et des autres îles austro-africaines de l'océan indien. Annales des Science Naturelle, Botanique. serie 6 9: 291-380.
Brotherus VF. 1925. Musci (Laubmoose), 2. Hälfte. In: Engler A, ed. Die natürlichen Pflanzenfamilien, ed. 2, 11: 73-75. Leipzig.
Churchill SP, Buck WR. 1982. A taxonomic investigation of Leptotheca (Rhizogoniaceae). Brittonia 34: 1-11.
Crum H. 1994. Rhizogoniaceae. In: Sharp AJ, Crum H, Eckel PM, eds. The Moss Flora of Mexico. Memoirs of the New York Botanical Garden 69: 588-590.
Eddy A. 1996. A Handbook of Malesian Mosses. Volume 3. Splachnaceae to Leptostomataceae. London: HMSO.
Koponen T, Touw A, Norris DH. 1986. Bryophyte flora of the Huon Peninsula, Papua New Guinea. XIV. Rhizogoniaceae (Musci). Acta Botanica Fennica 133: 1-24.
Magill RE. 1987. Bryophyta. Part 1 Mosses. Fascicle 2: Gigaspermaceae-Bartramiaceae. In: Leistner OA, ed. Flora of Southern Africa. South Africa: Pretoria
Manuel MG. 1980. Miscellanea bryologica II. Classification of Rhizogonium Brid., Penzigiella hookeri Gangulee, and some nomina nuda. Cryptogamie, Bryologie. Lichénologie 1: 67-72.
Manuel MG. 1981. Synopsis of the Rhizogoniaceae Broth. in Malaya. Cryptogamie, Bryologie. Lichénologie 2: 449-455.

TBG49/rhiz Issue 1 - 27.02.97