Hattoria 6: 75－91, 2015 A Taxonomical Synopsis of Brotherella (Pylaisiadelphaceae, Bryopsida) Yu Jia1 and Benito C. Tan2 1 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China 2 The University and Jepson Herbaria, University of California at Berkeley, Berkeley, CA, U.S.A. 94720 Abstract. The genus Brotherella M. Fleisch. is a member of the Pylaisiadelphaceae and many of the species are distributed in East Asia. A few species have been reported from Europe, North and Central America. Since Fleischer proposed the genus Brotherella in 1914, sixty five taxa have been described. Fifteen species of Brotherella are accepted after the revision: Brotherella canadensis W.B. Schofield, B. complanata Reimers & Sakurai, B. curvirostris (Schwägr.) M. Fleisch., B. cuspidata Y. Jia & J.-M. Xu, B. deplanatula (Cardot) Broth., Brotherella erythrocaulis (Mitt.) M. Fleisch., B. falcata (Dozy & Molk.) M. Fleisch., B. fauriei (Cardot) Broth., B. henonii (Duby) M. Fleisch., B. longipes Broth., B. luzonensis (Broth.) M. Fleisch., B. minutula E.B. Bartram, B. nictans (Mitt.) Broth., B. opaeodon (Sull.) Broth. and B. recurvans (Michx.) M. Fleisch. Brotherella crassipes Sakurai, B. herbacea Sakurai, B. indosinensis (Broth. & Paris) Broth. and B. roellii (Renauld & Cardot) M. Fleisch. are proposed to be new synonyms. Brotherella luzonensis (Broth.) M. Fleisch. is reported new to China, while Brotherella erythrocaulis (Mitt.) M. Fleisch. and B. fauriei (Cardot) Broth. are reported for the first time in North America. A key to the species is provided. Introduction Brotherella is genus named in honor of Finn bryologist, V. F. Brotherus. Species of Brotherella commonly grow on tree trunks and decaying logs in forest. For many years since its inception, the genus has proven difficult to define at the species level because of the morphological polymorphism exhibited in some species and the overlapping of taxonomic characters observed between species. Sixty-five names were attributed to the genus from the time of M. Fleischer (1914) to Wijk et al. (1969). At the time of current revision, thirty-six legitimately published species names were in circulation (Redfearn et al., 1996; Crosby et al., 1999; Tan & Jia, 1999; Jia, 1999; Jia & Xu, 2006; Schofield, 2006, 2014; Jia et al., 2006, 2007; Jia and He, 2010). Phytogeographically, the genus is a temperate taxon, with a few species extending to the tropical regions. Five geographical areas of distribution of species of Brotherella can be recognized: 1) Eastern Asia to South Asia; 2) Pacific Islands; 3) Europe; 4) North America, 75 and 5) Central America. To date, there is no report of Brotherella from Africa, South America, and Australia and New Zealand. Eastern Asia, where two-third of the species of Brotherella are distributed, is apparently the diversity center of Brotherella in the world. Below is a synopsis of our revised species concepts based on a renewed taxonomic study. Many of the accepted synonymy follows Iwatsuki (2004). A full monograph with detailed species description and complete citation of synonymy and specimens studied will follow. We believe that our abridged summary presented below, which includes new synonymy, new species records and new illustrations of two species helps clarify the confusing taxonomy of this genus. We like to receive feedback from readers using the new key to the species and their taxonomic comments for the improvement of our preparation of a worldwide monograph for the genus Brotherella. The arrangement of the taxa in this treatment is alphabetical by the species epithet for ease of reference. Brotherella M. Fleisch., Nova Guinea 12, Botanique Livr. 2: 119. 1914. Type species: Brotherella lorentziana (Molendo ex Lorentz) Loeske ex M. Fleisch. (see also Section of Uncertain Taxa for the synonymy of B. lorentziana). As a genus, Brotherella is best distinguished by a somewhat glossy and complanate plant appearance, slightly differentiated stem and branch leaves, a basal row of distinctly inflated alar cells, toothed leaf apices, and exothecial cell walls only longitudinally thickened. The similar alar cell organization, among other diagnostic characters mentioned above, observed in all species after the revision, seems to indicate that this genus is a natural group, but a recent phylogenetical grouping of taxa based on rbcL gene sequences shows that it is still a paraphyletic genus (Suzuki et al., 2013). Further study and delineation of the genus combining the morphological and molecular characters are needed. The genus has also been recombined at one time with Pylaisiadelpha Cardot (Buck 1984). The differences between these two genera have been clarified by Ando et al. (1989). For a brief history of this genus, see Tan and Jia (1999). Recent molecular phylogenetic studied also show a close relationship of this genus with Pylaisiadelpha Cardot and its allied genera, and supported the placement of Brotherella in the segregate family Pylaisiadelphaceae (Goffinet et al. 2008; Tsubota et al. 2000). In the family Pylaisiadelphaceae, some members of Wijkia H.A. Crum can be confused for species of Brotherella. However, species of Wijkia has bi- to tripinnately branching system with much differentiated stem and branch leaves. Compared to species of Brotherella, the alar cells of Wijkia also are larger in size and much inflated. Likewise, in the family Sematophyllaceae sensu stricto, a few species of Sematophyllum with large, inflated alar cells approximate Brotherella in their alar organization. But species of the former genus have nearly entire perichaetial leaf margins and strongly collenchymatous exothecial cells, while members of the latter genus have toothed perichaetial leaf margins and semi-collenchymatous exothecial cells. Species of Brotherella usually grow on tree trunks or rotten logs, occasionally on stones, in various types of forests at high elevation. The genus mainly distributes in Eastern Asia, with a few species in Europe, North and Central America. 76 An artificial key to accepted species of Brotherella 1. Branch leaves predominantly strongly cuspidate ················································ B. cuspidata 1. Branch leaves predominantly acute, short to long acuminate ··············································· 2 2. Plants predominantly regularly and pinnately branched, leaves broadest near the base ················ ····································································································· B. curvirostris 2. Plants predominantly subpinnately or irregularly branched, leaves broadest not near the base ····· 3 3. Ratio of length and width of median leaf cells more than 20:1 ································ B. opaeodon 3. Ratio of length and width of median leaf cells less than 16 (18): 1 ········································ 4 4. Stem and branch leaves mostly entire, ratio of length and width of stem and branch leaves more than 6:1 ······························································································ B. minutula 4. Stem and branch leaves mostly strongly toothed, serrulate or denticulate, ratio of length and width of leaves less than 5:1 ························································································· 5 5. Plants large, pendulous, stem and primary branches long creeping, often forming a long slender terminal ·································································································· B. falcata 5. Plants small to medium in size, not pendulous, stems and primary branches not long creeping, not forming a long slender terminal ······························································· 6 6. Stem and branch leaves mostly broadly ovate to ovate-lanceolate, acute to short acuminate; the narrow acumen mostly less than 1/4 the length of leaf ···················· 7 6. Stem and branch leaves mostly oblong-lanceolate, long acuminate; the narrow acumen mostly more than 1/4 to 1/2 the length of leaf ··············································· 13 7. Stem and branch leaves mostly strongly toothed to serrulate above ·························· 8 7. Stem and branch leaves mostly denticulate to nearly entire ··································· 10 8. Stem and branch leaves mostly falcate-secund; inner perichaetial leaves narrowly lanceolate ············································································ B. luzonensis 8. Stem and branch leaves mostly erect, slightly falcate; inner perichaetial leaves ovate- lanceolate ·························································································· 9 9. Terminal branches slightly complanate; branch leaves ovate-lanceolate; seta more than 3 cm long ·························································································· B. henonii 9. Terminal branches complanate; branch leaves narrowly ovate-lanceolate; seta to about 1.5 cm long ················································································· B. complanata 10. Leaf acumens mostly strongly falcate-secund ·············································· 11 10. Leaf acumens mostly not falcate-secund ···················································· 12 11. Leaf supra alar cells differentiated, 3－5, enlarged; inner perichaetial leaves ovate- lanceolate ··············································································· B. recurvans 11. Leaf supra alar cells not well differentiated; inner perichaetial leaves narrowly lanceolate