Bot. Bull. Acad. Sin. (1995) 36: 143-153

Chiang — Phylogeny of Macrothamnium

Phylogeny and morphological evolution of Macrothamnium M. Fleisch. and related taxa (Bryopsida: Hypnaceae)

Tzen-Yuh Chiang

Institute of Botany, Academia Sinica, Taipei, Taiwan 115, Republic of China

(Received February 27, 1995; Accepted June 5, 1995)

Abstract. Three species of Macrothamnium M. Fleisch., two species of Leptohymenium Schwaegr., two species of Leptocladiella M. Fleisch., and one species of Orontobryum M. Fleisch. were revised. Macrothamnium submacrocarpum Renauld & Cardot and M. longirostre Dix. were synonymized with M. macrocarpum (Reinw. & Hornsch.) M. Fleisch. Macrothamnium hylocomioides M. Fleisch. and Chaetomitriopsis diversifolia Zanten were considered identical to M. javense M. Fleisch. A new combination, Hypnum flagellaris (T. J. Kop. & D. H. Norris) T.Y. Chiang, was proposed and excluded from genus Leptocladiella. The phylogeny of Macrothamnium and the related genera was reconstructed based on ontogenetic transformations of paraphyllia, axillary hairs, central strand, and other morphological characters. Whole ontogenetic transformations, instead of instantaneous stages, were recognized as characters and polarized by outgroup comparison. To test the phylogenetic relationship (familial position), Hypnum lindbergii Mitt. and Gollania ruginosa (Mitt.) Broth. of the Hypnaceae and Hylocomium splendens (Hedw.) B.S.G. and Loeskeobryum cavifolium (Lac.) M. Fleisch. of Hylocomiaceae were chosen as outgroups. The monophyly of the clade of Macrothamnium, Leptohymenium, and Orontobryum was supported, with a bootstrapping value of 96%, and was characterized by sharing regularly pinnate branching pattern, amplified costa, and a lack of foliose pseudoparaphyllia, whereas Macrothamnium appeared to be a paraphyletic group, in which M. leptohymenioides Nog. is more related to Leptohymenium than it is to any other species of Macrothamnium. The three genera are more related to the Hypnaceae than to the Hylocomiaceae. In contrast, Leptocladiella appears to be a genus of Hylocomiaceae. Patterson's tests were applied to the homology of the horn-type paraphyllia of Hylocomium splendens and Loeskeobryum cavifolium, and the foliose-type paraphyllia of Orontobryum hookeri. They passed the similarity and conjunction tests, but failed the congruence test. This suggests that the two types of paraphyllia are homoplastic—that is, they evolved independently rather than being derived from a most recent ancestor.

Keywords: Homology; Macrothamnium; Monophyly; Ontogenetic transformations; Paraphyllia; Patterson's three tests; Phyllodioicous.

defined by weft growth-form. In delimiting the genera of the Hypnaceae, Nishimura et al. (1984) adopted Andrews' and Noguchi's concepts, and classified Macrothamnium, Leptocladiella, and Leptohymenium as Hypnaceae and Orontobryum as Hylocomiaceae by using the presence or absence of paraphyllia to distinguish them.

Buck and Vitt (1986) criticized the sole use of paraphyllia in defining the Hylocomiaceae as illogical. In their so-called `pseudo-cladistic analysis', which was performed by arbitrary and empirical interpretation of morphological characters and taxonomic relationships of pleurocarpous mosses, they characterized the Hylocomiaceae by serrate leaf-margins, amplified costa, and reticulate exostome ornamentation. They classified Macrothamnium, Leptocladiella, Leptohymenium, and Orontobryum as Hylocomiaceae.

Buck and Crum (1990), in an evaluation of familial limits of Thuidiaceae and Leskeaceae, re-emphasized paraphyllia in defining the Hylocomiaceae and transferred genera Hylocomiopsis and Actinothuidium into the Hylocomiaceae. This classification has increased the complexity of the circumscription of the Hylocomiaceae and related families.


The genera Macrothamnium, Leptocladiella, Leptohymenium, and Orontobryum are distributed mainly in the montane regions of southeastern Asia, with one exception—Leptohymenium tenue (Hook.) Schwaegr., which was reported in the New World (Mexico) (Rohrer, 1985b, 1986). According to the fossil record of a Macrothamnium sp. found in Poland, the origin of the taxa can be traced to the Miocene (Miller, 1984).

The close relationship of Macrothamnium, Leptohymenium, and Orontobryum has been interpreted in Rohrer's cladistic study on the Hylocomiaceae (Rohrer, 1985a), based on eighteen morphological characters. He recognized Leptocladiella as a genus more distantly related to the above taxa, although many other bryologists had synonymized it either to Leptohymenium (Andrews, 1954) or to Macrothamnium (Noguchi, 1972a).

The taxonomic position of the taxa is a controversial issue. There has been conjecture about the familial position of Macrothamnium, Leptocladiella, Leptohymenium, and Orontobryum. Rohrer (1985b) recognized twelve genera, including the above four taxa, in the Hylocomiaceae,

Botanical Bulletin of Academia Sinica, Vol. 36, 1995

Nishimura et al. (1984) and Buck and Crum (1990) suggest that paraphyllia in the Hylocomiaceae is homologous and useful for classification, but Buck and Vitt (1986) and Rohrer (1985a) describe the homology as false. In my opinion, the homology remains unproven. To test it, I studied the ontogeny of paraphyllia in this group and conducted a cladistic analysis.

In this paper, I focus on the phylogenetic reconstruction of Macrothamnium, Leptohymenium, Orontobryum, and Leptocladiella. I adopt the character concept of Chiang and Larson (1995), in which the whole ontogenetic transformation is recognized, rather than just the instantaneous characters of the adult-stage. The monophyly of the taxa is tested by cladistic analysis and statistical tests.

Macrothamnium, Leptocladiella, Leptohymenium, and Orontobryum share several morphological characters—they lack foliose pseudoparaphyllia and have branching patterns and serrate leaf-margins. Rohrer (1985b) recognized five species in Macrothamnium, two taxa in Leptocladiella, two species in Leptohymenium, and one taxon in Orontobryum. Koponen and Norris (1985) published a new species of LeptocladiellaL. flagellaris. Reviews of taxonomic history can be consulted in Noguchi (1972a, b) and Rohrer (1985b).

Phylogenetic Analyses

Ingroup and Outgroup

Three species of Macrothamnium, two species of Leptohymenium, two species of Leptocladiella, and one species of Orontobryum were examined. To polarize the characters more precisely, Hypnum lindbergii and Gollania ruginosa of the Hypnaceae and Hylocomium splendens and Loeskeobryum cavifolium of the Hylocomiaceae were chosen as outgroups (Appendix 1).

The specimens deposited in the herbaria of Missouri Botanical Garden (MO), the British Museum (BM), Farlow Herbarium (FH), Hattori Botanical Laboratory (NICH),

Leiden (L), and Hiroshima University (HIRO) were examined.

Characters Examined

Twenty-six characters were included in this analysis. All possible characters were studied, except for peristomes, which can be observed only in culture. Not all characters transform; the characters for which developmental changes were described are paraphyllia, central strand, and axillary hairs. The ontogenetic transformations were studied and sequenced by observing different stages in individuals —from stem apices to mature parts with inflorescences. The initial ontogenetic stage (usually of a single cell) was examined at the apical, meristematic cells of young innovation. The series of transformations was interpreted based on the principle of ontogenetic change in structure from simple to complicated, in terms of cell number or branching pattern.

The concept of character used in this paper primarily follows that of Chiang and Larson (1995), in which the whole transformation, rather than individual stages (Mishler and de Luna, 1991) was recognized as characters. Character states were polarized by outgroup comparison (Maddison et al., 1984) based on the genera Hypnum, Gollania, Hylocomium, and Loeskeobryum (Table 1). One of the characters used in Rohrer's (1985a) analysis—life-form—is not included in this study, because it is a subjective classification by bryologists. For example, Crum and Anderson (1981) say that the plants of Hylocomium splendens grow in loose mats, and those of Rhytidium ruginoa grow in tufts, whereas Rhorer (1985a) describes the life-form of both taxa as wefts. According to my own observation, there is no clear-cut boundary between weft and mat life-forms. The characters included in this analysis and the polarization of charracter states follow:

1. Paraphyllia: Paraphyllia are absent (state 3) in most taxa of Macrothamnium complex and the Hypnaceae.

Table 1. Distribution and polarization of characters and character-state for Macrothamnium complex and outgroups in cladistic analyses.

Taxa characters 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6

Gollania ruginosa 3 0 0 0 0 0 0 1 0 0 0 0 0 0 2 2 0 0 0 0 0 0 1 0 0 0

Hypnum lindbergii 3 0 0 0 0 0 0 1 0 0 0 0 0 0 0 2 1 0 0 0 0 1 1 1 0 1

Hylocomium splendens 1 2 2 1 0 0 1 0 0 0 0 2 0 0 1 0 2 0 1 1 0 0 0 0 0 1

Loeskeobryum cavifolium 0 2 1 1 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 1

Macrothamnium macrocarpum 3 2 0 1 0 0 0 1 0 0 0 1 0 0 2 2 3 0 2 1 1 0 1 1 0 1

M. javense 3 2 0 1 0 0 0 1 0 0 0 1 0 0 2 2 3 1 2 1 1 0 1 1 0 1

M. leptohymenioides 3 2 0 1 1 1 0 1 1 2 0 1 0 0 2 2 3 0 2 1 1 0 1 1 1 1

Leptohymenium tenue 3 2 0 1 1 1 1 2 2 2 1 1 0 0 2 2 3 0 0 1 0 0 1 1 1 1

L. hokinense 3 2 0 1 1 1 * 2 2 2 1 0 0 0 2 2 3 0 1 1 0 0 1 1 1 1

Orontobryum hookeri 2 1 0 0 1 1 0 1 2 2 1 1 0 0 0 2 1 0 2 1 1 0 1 1 2 1

Leptocladiella psilura 3 2 2 1 0 1 1 1 0 1 0 0 1 1 3 2 0 0 0 1 0 1 1 1 0 1

L. delicatula 3 2 1 1 0 1 1 1 0 1 0 0 0 1 3 2 3 0 0 1 0 1 1 1 0 1

(* data not available).

Chiang — Phylogeny of Macrothamnium

Three types of paraphyllia—ox-horn type (state 0), deer-horn type (state 1), and foliose type (state 2)—are present in Loeskeobryum, Hylocomium,and Orontobryum respectively.

2. Pseudoparaphyllia: Pseudoparaphyllia are not differentiated (state 2) in most taxa of Macrothamnium complex and the Hylocomiaceae. A foliose type (state 0) occurs in the Hypnaceae, i.e. Hypnum and Gollania. Orontobryum has pseudoparaphyllia of `curious leaf' type (Noguchi, 1972b) (state 1).

3. Central strand of stems and branches: Central strands are absent (state 2) in Hylocomium and Leptocladiella psilura. According to the timing of differentiation in the stem, two types can be observed: early type (state 0) in the Hypnaceae and most taxa of Macrothamnium complex and late type (state 1) in Loeskeobryum and Leptocladiella delicatula.

4. Growth form: Orontobryum, Hypnum, and Gollania have monopodial (state 0) growth-form. In contrast, other taxa in this study have sympodial (state 1) growth-form.

5. Capsule inclination: Capsules are inclined or subinclined (state 0) in most taxa and the outgroup. Erect capsules (state 1) were observed in Macrothamnium leptohymenioides, Leptohymenium, and Orontobryum.

6. Annulus: Annulus are absent (state 1) in Leptocladiella, Leptohymenium, Orontobryum, and Macrothamnium leptohymenioides, and are differentiated (state 0) in other taxa.

7. Operculum: Conic operculum (state 0) was observed in Macrothamnium, Orontobryum, and the Hypnaceae. Rostrate operculum (state 1) occurs in Leptohymenium, Leptocladiella, and the Hylocomiaceae.

8. Exostome ornamentation: Three types of ornamentation on exostome were observed: reticulate type (state 0) in Hylocomium; cross-striate type (state 1) in Gollania, Hypnum, Loeskeobryum, Macrothamnium, Leptocladiella, and Orontobryum; and smooth type (state 2) in Leptohymenium.

9. Segments of endostome: Broad segments with perforations (state 0) were observed in Macrothamnium macrocarpum, M. javense, Leptocladiella, and four outgroup taxa; linear segments with perforations (state 1) occur in M. leptohymenioides; and imperforate segments (state 2), often poorly developed, were observed in Leptohymenium and Orontobryum.

10. Cilia: In most taxa, endostome are well differentiated, with more than three cilia (state 0) in each capsule. One or two cilia (state 1) were observed in Leptocladiella. Cilia are not differentiated in Orontobryum and Leptohymenium (state 2).

11. Stem- and branch-leaves: Stem- and branch-leaves are differentiated (state 0) in most ingoup taxa and four outgroup taxa, and are not differentiated (state 1) in Leptohymenium and Orontobryum.

12. Apex of stem-leaf: Apex of stem-leaf is tapering (state 0) in Gollania, Hypnum, Loeskeobryum,

Leptocladiella, and Leptohymenium hokinense. Apiculate apices (state 1) of stem-leaves were observed in Macrothamnium, Orontobryum, and Leptohymenium tenue. In contrast, crimped apices (state 2) of stem-leaves occur in Hylocomium.

13. Costa number of branch-leaf: Most taxa have double costae (state 0) in branch-leaf. In Leptocladiella psilura, costae are forked (state 1).

14. Costal spine: Costal spines were observed (state 1) on leaves of Leptocladiella. In most taxa, costal spines are not differentiated (state 0).

15. Cell papillosity: Cell walls are smooth (state 0) in Hypnum, Loeskeobryum, and Orontobryum. In Gollania, Macrothamnium, and Leptohymenium, cell ends project slightly (state 2). In Hylocomium, cell ends project strongly (state 1). Regular-sized cell ends mixed with some enlarged papilla at the corner of cells (state 3) were observed in Leptocladiella.

16. Leaf-base: Three types of leaf-base were observed: 0, not decurrent (in Hylocomium); 1, auriculate (in Loeskeobryum); 2, decurrent (in most other taxa).

17. Branching pattern of plants: Four types are coded: 0, 1' irregularly pinnate; 1, 1' regularly pinnate; 2, 2'_3' regularly pinnate; 3, 2'_3' irregularly pinnate.

18. Dwarf males: Dwarf males occur (state 1) in Macrothamnium javense, and are absent (state 0) in other taxa.

19. Costa length: Three types of costa length were observed: 0, shorter than half; 1, longer than half; 2, variable.

20. Leaf shape: In Hypnum lindbergii and Gollania ruginosa, leaves are falcate (state 0). In the ingroup taxa and the Hylocomiaceae, leaves are erected (state 1).

21. Leaf margins: In Macrothamnium and Orontobryum, leaf margins are serrate (tooth consisting of more than one cell, state 1). In other taxa, leaf margins are serrulate (tooth consisting of one cell, state 0).

22. Epidermal cells of stem: Two states were coded: 0, not enlarged (in most taxa); 1, enlarged (in Hypnum and Leptocladiella).

23. Neck of leaf: Neck of leaf is present (state 0) in Hylocomium and Loeskeobryum, and is absent (state 1) in most other taxa.

24. Axillary hairs: Three apical cells (state 1) were observed on axillary hairs in the ingroup taxa, Loeskeobryum, and Hypnum. In Gollania and Hylocomium, five apical cells (state 0) were observed at terminal stage.

25. Spore size: Most taxa have spores approximately 20 µm in diameter (state 0). Leptohymenium and Macrothamnium leptohymenioides have larger spores (20_30 µm) (state 1). The diameter . of spores in Orontobryum is larger than 30 µm (state 2) (Rohrer, 1985).

26. Leaf orientation: The leaves of Gollania ruginosa are falcate-secund (state 0). Other taxa have heteromallously oriented leaves (state 1).

Botanical Bulletin of Academia Sinica, Vol. 36, 1995

Cladistic Analysis

Cladistic analyses of the ontogenetic data and other morphological characters were conducted using the exhaustive searches of the PAUP computer program (Version 3.1.1, Swofford, 1993). A strict consensus tree and a 50% majority-rule consensus tree rooted at outgroups were identified. All characters were unweighted.

The reliability and accuracy of clades in cladograms was tested using bootstrap resampling with 400 replicates (Felsenstein, 1985). A g1 test (Huelsenbeck, 1991) of skewed tree-length distribution was calculated from 1,000 random trees generated by the PAUP program to evaluate the phylogenetic information content of the data. Critical values of g1 are given in Hillis and Huelsenbeck (1992). The fit of character data to phylogenetic hypotheses was evaluated using consistency index (CI) (Kluge and Farris, 1969) and retention index (RI) (Farris, 1989). The statistical significance of CI was determined according to Klassen et al. (1991).

Based on inferred phylogeny, the morphological evolution was analyzed using the MacClade computer program (Maddison and Maddison, 1992). The homology of characters, such as paraphyllia and peristomes, was tested following Patterson's methodology (Pattersons, 1982), i.e. similarity, conjunction, and congruence tests.

Results and Discussion

Ontogenetic Transformations of Morphological Characters

A) Paraphyllia: Paraphyllia are differentiated in only three of the species examined. Three types of adult-stage paraphyllia were observed: ox-horn type (Loeskeobryum cavifolium, Figure 1A: a-f), deer-horn type (Hylocomium splendens, Figure 1A: a-g), and foliose type (Orontobryum, Figure 1B: a-g) (cf. Noguchi, 1972a, b; Rohrer, 1985a). The first two types are more similar than either is to the third type.

All developmental transformations initiate with a single, lanceolate cell (Figure 1A: a and 1B: a) followed by a two- or three-cell `hair-like' stage which develops via an elongation process (Figure 1A: b-c; 1B: b-c). In ox-horn and deer-horn types, branching is the next process, in which `hairs' transform into a `forked' stage (Figure 1A: d). The basal cells of `forked' paraphyllia then divide into two rows (Figure 1A: e). The development of the ox-horn type ends at this stage. In deer-horn paraphyllia, the basal cells continue dividing into three or four rows (Figure 1A: f), and the paraphyllia keep branching and develop three or four `arms' (Figure 1A: g).

In foliose paraphyllia, the branching process is absent. The basal cells of the hair-like structure divide into two rows (Figure 1B: d). By a series of divisions, the paraphyllia arrive at a `foliose' terminal stage (Figure 1B: e-g).

B) Central strands: central strands are conducting tissue originating from the apical cells of stems or branches, and if present, can be classified into two types, early and late, according to the timing of differentiation.

Figure 1. Ontogenetic transformations of paraphyllia: A) horn-type a, paraphyllia initial; b and c, elongating; d_f, branching, ox-horn type (Loeskeobryum); g, broadening basal portion, deer-horn type (Hylocomium); B) foliose-type (Orontobryum): a, paraphyllia initial; b_d, elongating; e_g, foliating. [all ×250, drawn from Koponen 19258 (Loeskeobryum cavifolium), Redfearn & Su 745 (Hylocomium splendens), and Griffith s. n. (Orontobryum hookeri)].

Figure 2. Ontogenetic transformations of central strands: A and B) central strands absent; A, C, and D) differentiation of central strands; 1_3 (on bottom): states of ontogeny of central strands: 1, absent (Hylocomium splendens, drawn from Redfearn & Su 745); 2, early central strand (Macrothamnium macrocarpum, drawn from Chiang 20318); and 3, late central strand (Leptocladiella delicatula, drawn from Zhang 467). (A_D. ×250).

Chiang — Phylogeny of Macrothamnium

a. `Early' type (Figure 2-2): The central strands of stems are differentiated from the tip of apical cells. No transformations are observed in this type. Early central strands occur in most taxa.

b. `Late' type (Figure 2-3): The central strands are not differentiated at stem apices. This type occurs in Loeskeobryum cavifolium and Leptocladiella delicatula.

c. Absent (Figure 2-1): In Hylocomium splendens and Leptocladiella psilura, central strands are not differentiated.

C) Axillary hairs: The transformations of axillary hairs (Figure 3) began with a basal, colored cell (Figure 3: a).

The basal cell may divide into a two-cell stage and give rise to apical cells (Figure 3: a-e). Most taxa examined had three apical cells, except for Gollania ruginosa and Hylocomium splendens, which had five apical cells.

Phylogenetic Inference

A strict consensus of three equally most-parsimonious trees (Figure 4), with a length of 56 steps, a consistency index (CI) of 0.732 (p<0.01), and a retention index (RI) of 0.727, was identified rooted at Hylocomium, Loeskeobryum, Hypnum, and Gollania. A g1 statistic of 0.591 indicated a significant amount of phylogenetic signal in the ontogenetic and morphological data.

The monophyly of Macrothamnium, Leptohymenium, and Orontobryum—a sister clade to Hypnum and Gollania—is significantly supported by a bootstrap value of 96% (Figure 5). That is, these three genera are more closely related to the Hypnaceae than to Hylocomiaceae. This clade is characterized by sharing regularly pinnate branching pattern and amplified costa, and by lacking foliose pseudoparaphyllia. Genus Macrothamnium, however, is revealed to be a paraphyletic group, in which M. leptohymenioides is more related to Leptohymenium and Orontobryum than it is to other taxa of Macrothamnium because of a lack of shared derived characters. The clade of Leptohymenium and Orontobryum is characterized by having erect capsules with reduced endostomes. Within this clade, the most parsimonious tree shows that

Figure 3. Ontogenetic transformations of axillary hairs: a, Basal cells; b_d, 1- to 3-cell stage; e, 4-cell stage; f, 5-cell stage. (drawn from Redfearn & Su 745, Hylocomium splendens).

Figure 5. The strict consensus tree of Macrothamnium, Leptohymenium, and Orontobryum rooted at Hypnum and Gollania: A) inclined capsules with well-differentiated cilia; B) erect capsules, cilia absent; 1, endostome well-differentiated; 2, endostome incomplete; 3, endostome residual. Numbers at nodes are bootstrapping values.

Figure 4. The strict consensus tree of Macrothamnium and related taxa rooted at Hylocomiaceae and Hypnaceae. /: paraphyllia. A) ox-horn type; B) deer type; C) foliose type). Numbers at nodes are bootstrapping values.

Botanical Bulletin of Academia Sinica, Vol. 36, 1995

Macrothamnium appears to be a paraphyletic group according to the above analysis since no derived characters are able to differentiate M. macrocarpum and M javense from other taxa (M. leptohymenioides, Leptohymenium, and Orontobryum). To transfer Leptohymenium and Orontobryum to Macrothamnium nomenclaturally is one of the possible ways to resolve the taxonomy of this complex. Nevertheless, the main purpose of this paper is to generate a testable phylogenetic hypothesis, which appears to agree with Rohrer's (1985a) analysis at generic level. Before more biological evidence of this complex is accumulated, such as the molecular systematics and biology of adaptation, it is not valid to make any nomenclatural change. I would leave Macrothamnium to be a paraphyletic group in the following taxonomic treatment. Further research and evidence are needed for testing the paraphyly hypothesis of Macrothamnium.

Key to the Species of Macrothamnium, Leptocladiella, Leptohymenium, and Orontobryum

1. Paraphyllia present; plants monopodial............................ .......................................................Orontobryum hookeri

1. Paraphyllia absent; plants sympodial.......................... 2

2.Capsule suberect, horizontal, or inclined; endostomal cilia present 3

3. Males dwarf .....................Macrothamnium javense

3. Males normal-sized 4

4. Spinous projection of laminal cells absent..... .........................Macrothamnium macrocarpum

4. Spinous projection present at ends of laminal cells...... .......... 5

5. Central strands absent throughout onto-genetic transformations, branch leaves lanceolate...................Leptocladiella psilura

5. Central strands present at adult stage only, branch leaves ovate........................................ ................................Leptocladiella delicatula

2. Capsule erect; endostomal cilia absent 6

6. Exostome ornamentation cross-striate...... ...........Macrothamnium leptohymenioides

6. Exostome ornamentation smooth 7

7. Leaves broad-ovate................................ ...........................Leptohymenium tenue

7. Leaves lanceolate. ................................. ...................Leptohymenium hokinense

I. MACROTHAMNIUM M. Fleisch., Hedwigia 44: 307. 1905. Type species: Hypnum macrocarpum Reinw. & Hornsch.

1. Macrothamnium leptohymenioides Nog., Kumamoto J. Sci. Biol. 11: 6. 1972.—TYPE: Nepal, Tokyo Univ. Exped. n. 237772 (holotype: NICH).

Orontobryum recurvulum Gangulee, Mosses E. India 6: 1506. f. 754. 1977.—TYPE: Bhutan, Griffith 130 (holotype: BM; isotype: FH).

Leptohymenium is a monophyletic group characterized by cell papillosity pattern and crenulate leaf-margins; a close relationship between Leptocladiella and the other genera treated in this paper is not supported. Based on a cladistic analysis of morphological and ontogenetic characters, Leptocladiella is a genus of Hylocomiaceae.

Homology of Paraphyllia

Horn-type and foliose-type paraphyllia share similar ontogenetic transformations. No two individuals or species had both horn-type and foliose-type paraphyllia, and thus they passed Patterson's (1982) similarity and conjunction tests.

No exclusive clade (of Hylocomium , Loeskeobryum and Orontobryum), however, is characterized by paraphyllia. The reconstructed phylogeny suggests that Orontobryum is more related to Macrothamnium than it is to other taxa with paraphyllia. Patterson's congruence tests of the homology hypothesis failed. In conclusion, the hypothesis of homology of the paraphyllia in Hylocomiaceae and Orontobryum is false. The paraphyllia in Orontobryum are likely to have evolved independently from those of other taxa.

Reductive Evolution of Sporophytic Characters in the Macrothamnium Complex

The sporophytic structures in Macrothamnium complex are homologous according to Patterson's three tests. A nested hierarchical relationship of capsule inclination, endostomes, and cilia is supported (Figure 5). A transformation is observed from inclined and well-differentiated capsules in Macrothamnium, through erect capsules with incomplete endostomes in M. leptohymenioides, to erect capsules with residual endostomes in Leptohymenium and Orontobryum. It has been hypothesized that the erect capsules correlate with corticolous (Grout, 1903) or xerophytic habitats (Vitt, 1981). Since these taxa are elements of temperate forests, the association with xerophytic habitats does not hold. In addition, the literature (e.g. Rohrer, 1985b) and collection records of herbarium specimens do not support the hypothesis of obligatory epiphytes for this group.

From the ontogenetic sequence, erect capsules are a stage prior to the curvation of capsules. Phylogenetically erect capsules are a derived state, but retain juvenile morphology by truncating development (paedomorphosis). The change in inclination of capsules may be an adaptation associated with the function of spore dispersal. On the other hand, the erect capsules may constrain the development of peristomes.

Taxonomic Treatment

Three species of Macrothamnium, two species of Leptohymenium, two species of Leptocladiella, and one species of Orontobryum are recognized. Leptocladiella flagellaris T. J. Kop. and D. H. Norris is synonymized to Hypnum.

Chiang — Phylogeny of Macrothamnium

This species is gametophytically identical to Macrothamnium macrocarpum, but it lacks endostomal cilia, a feature that links it to Leptohymenium tenue (Hook.) Schwaegr. Macrothamnium leptohymenioides is placed in Macrothamnium on the basis of its stem central strand and irregularly cross-striolated peristome teeth. This species is especially close to the `submacrocarpum' expression of M. macrocarpum.

Distribution. Myanmar, Nepal, Bhutan and China (Tibet).

Additional specimens examined. BHUTAN: Griffith 735 (MO, BM, FH), 756, 144 (BM), 736 (FH); Iwatsuki 1844 (FH); Mills et al. s.n. (FH). BIRMA: Sheriff & Taylor 3846b (BM). TIBET: Dixon 3847 (BM).

2. Macrothamnium macrocarpum (Reinw. & Hornsch.) M. Fleisch., Hedwigia 44: 308. 1905.

Hypnum macrocarpum Reinw. & Hornsch., Nov. Act. Acad. Caes. Leop. 14, Suppl.: 725. 1829.— SYNTYPE: Java, Malabaria, Mt. Gede, Reinwart s.n. (L).

Microthamnium submacrocarpon A. Jaeger ex Renauld & Cardot, Bull. Soc. R. Bot. Belg. 41: 99. 1905.

Macrothamnium submacrocarpum (Renauld & Cardot) M. Fleisch., Hedwigia 44: 308. 1905.—TYPE: Bhutan, inter Maria Basti & Labar, Durel s. n. (lectotype: BM), Sikkim-Himalaya, Decoly & Schaul s. n.; Sikkim, Kurz s. n. (all syntypes: BM), syn. nov.

Macrothamnium longirostre Dix., Rev. Bryol. Lichen. 13: 19. 1942.—TYPE: Japan, Sasaoka 4748 (holotype: BM).

Bryologists have over-emphasized the extreme forms of this variable species, and as a result, there has been a proliferation of names that are usually based on the examination of only a few specimens. In this species, leaf-shape is unreliable as a taxonomic character, since it varies greatly even within a single specimen. No clear-cut boundary can be drawn that separates these taxa. Even growth form varies greatly among specimens from different areas. The plants may branch either monopodially or sympodially, the leaf margins vary from serrulate to serrate, and the leaf-bases can be weakly to strongly decurrent. The capsules vary from suberect to inclined.

Distribution. Java, Philippines, Taiwan, Japan, China, Thailand, Nepal, Bhutan, India and Sri Lanka.

Additional specimens examined. JAVA: Fleischer s.n. (FH); Nyman 433. (MO); Schiffner 3896 (MO); Fleischer 349 (BM); Kurz 807 (BM); Junghuh s. n. (BM); Fleischer 349 (FH); Nyman 453 (FH); Warburg s. n. (FH). BORNEO: Kirthales s. n. (BM); Svihla 3377, 3610, 3429, 3423, 2797, 2777 (FH); Meijer 12700 (FH). PHILIPPINES: Tan & Aguila 81-28, Tan 74-214 (MO); Robinson 6596 (BM); Ramos 5966 (BM); Merrill 4878 (BM); Hadan 153, 158 (FM); Williams 81709 (FH). TAIWAN: Chiang 20318, 2500, 25324, 18951, 20609 (MO); Chuang s. n. (MO); Chiang s. n. (MO); Shimada,

s. n. (MO); Chuang & Schofield 597 (MO); Chuang 1390 (MO), 411, 396, 6217, 2038, 597, 4117, 5098, 5088 (FH); Sasaoka 3811 (BM). CHINA: Handel-Mazzetti 394c (BM); Chung 4081 (FH); Merril 10415 (FH); Redfearn, He & Su 516, 657, 198, 884a, 688, 806a (SMS). MALESIA: Henderson 23611 (BM); Clemens 33890 (FH). BIRMA: Dickason 8531, 8773, 7497, 7701, 8647, 9076, 9646, 9087, 9076, 9646, 9082, 8773, 8531, 8102, 7258,8647 (FH); Egerod 25 (FH). THAILAND: Touw 9194, 8836, 10701, 9680, 9165 (MO, FH), Hansen & Smitinand 13125 (MO); Kerr 18, 47 (BM); Smitinemd 8854 (FH); Wahdge & Carpenter 1500 (FH); Touw 9194, 8719, 8836, 11098 (FH). NEPAL: Iwatsuki 38 (MO); Dixon s. n. (BM); Norkett 6594, 6157 (BM); Stewart 14473 (FH); Falconer 737, 739 (FH); Duthie s. n. (FH); Kurz 2513 (FH); Weber 99341, 99443, 99408 (FH). INDIA: Fleischer 3228, 3230, 3074, 3073 (MO); Weir 5 (BM); Brotherus 3183 (BM); Oliver 1896 (BM); Berroter 407 (BM); Gough 72 12, 12, 7 (BM); Burkill 36533, 36544 (BM); Fischer s. n. (BM); Griffith 754 (BM); Shepheard 4 (BM); Norkett 11866 (BM); Bahadru s.n., 54 (BM); Dixon s.n. (BM); Hook 1057, 1059, 949 (BM); Gollan 2403 (BM); Brotherus s. n. (BM); Kurz 2150 (FH); Hiangulu 4973 (FH); Walker 453, 513, 489 (FH); Mitten s. n. (FH); Hooker s. n. (FH); Chopra & Abrul 456 (FH). BHUTAN: Griffiths s. n. (MO); Bartholomew 152 (MO); Falconer 737 (MO); Bobert s. n. (BM); Mecbold 16628, 16630 (BM); Levier s. n. (BM); Kurz 2406, 2418, 2397, s.n. (FH); Hooker 952, 981 (FH); Xavier 126 (FH). CEYLON: Thwaites 209 (MO, BM); Fleischer 448 (BM). HAWAII: Baldwin 138, 252 (FH).

3. Macrothamnium javense M. Fleisch., Hedwigia 44: 311. 1905.—TYPE: Java, Fleischer 348 (holotype: FH).

Macrothamnium hylocomioides M. Fleisch., Nova Guinea 12(2): 125. 1914. syn. nov.—TYPE: New Guinea, Niederl. Sudwest-Neu-Guinea: Am Goliath-Gebirge 1950-3000 m, Dekock 14 (lectotype: FH). Dekock 29 p.p. 33 p.p. (syntype: FH).

Chaetomitriopsis diversifolia Zanten, Nova Guinea Bot. 10: 316. 1964. syn. nov.—TYPE: New Guinea, Mt. Antares, Zanten 382 (holotype: L); Orion Mts., Tenmasigin, Vervoort 306 (paratype: MO).

Macrothamnium hylocomioides was separated from M. javense based on leaf-shape and inclination of capsules, but the characters are variable even within populations. No significant difference can be found that differentiates them as two species.

One of the most distinguishing characteristics of this species is its sexuality. Macrothamnium javense and M. hylocomioides were distinguished from other cladodioecious species by their phyllodioicous condition (Fleischer, 1905; Noguchi, 1972a). In this condition, the bud-like androecious plants are epiphytic on the leaves of normal-sized gynoecious plants (Wyatt, 1985). The presence of large and small spores was described in M. javense by Fleischer (1905). Noguchi (1972a) excluded the pos

Botanical Bulletin of Academia Sinica, Vol. 36, 1995

sibility of large spores in M. javense, arguing that they were nothing more than reproductive bodies of fungi. Some mosses, however, are amphispory (Mogensen, 1981; 1983)—a condition in which the ratio of large spores to small spores is variable. This condition has been reported in Pleurozium schreberi (Longton and Greene, 1979) and Plagiomnium medium (Newton, 1972). Small spores are believed to be abortive in the amphisporal condition. Unlike anisospory, in which the ratio of large spores to small spores is approximately 1, amphispory in Macrothamnium javense seems to be a character sensitive to ecological factors.

The geographical distribution is another interesting phenomenon in Macrothamnium. Macrothamnium macrocarpum is widely distributed in Japan, Taiwan, China, Indo-China, the Himalayas, India, Sri Lanka, Malesia, the Philippines, Borneo, and West Java. The distribution of M. javense is almost east of that of M. macrocarpum. The species overlap in the Philippines, Borneo, and Java. No significant difference of sporophytic and gametophytic characters, except sexuality, can be found in M. macrocarpum and M. javense. Dwarf males epiphytic on female plants is unique to M. javense. In the type specimen of M. javense, a detached branch with normal males was marked by Fleischer, although it was not reported in the original description of this species. Misplacement of that branch could explain the mix of sexualities in the same collection. On the other hand, M. macrocarpum might be sexually polymorphic among populations. The physiological and ecological adaptation of dwarf males to ecological factors has been studied in other mosses. Une (1985) showed that male dwarfness in anisosporous species such as Macromitrium is genetically determined, whereas in isosporous species, dwarfness is regulated by phytohormones from female plants. Furthermore, the male spores of isosporous Macromitrium have the potential to develop into either normal or dwarf males. The mechanism of expression of dwarf males in amphisporous species remains unknown.

According to the specimen records, the distribution of M. javense in Java is restricted to the eastern portion. It can be explained that there is a sympatric region of the two taxa in central Java. No other specimens with mixed sexualities have been found in Java. More evidence from field surveys and population genetics is needed to test the hypothesis of identity of M. macrocarpum and M. javense.

Chaetomitriopsis diversifolia was found in New Guinea. Zanten (1964) claimed that this species is related to Chaetomitrium, a genus of the Hookeriaceae. Chaetomitriopsis diversifolia is distinguished from Chaetomitrium by having paraphysis. The differentiation of stem- and branch-leaves, sympodial growth-form, and irregular branching pattern in C. diversifolia were not observed in other species of Chaetomitriopsis. Chaetomitriopsis diversifolia is a species of Macrothamnium and is synonymous with M. javense.

Distribution. Java, Borneo, Celebes, Philippines, and New Guinea.

Additional specimens examined. NEW GUINEA: Koponen 32955, Norris 59911 (MO); Carr 15215 (MO); de Sloover 42739 (MO); Weber & McVean 32180 (MO); Hoogland 9579 (FH); Hoogland & Scbodde 6930 (FH); Robbins 3414, 3152, 3032, 3044, 219, 217, 2770, 2776 (FH); Carr 15214 (FH); Nils & Gyld enstolpe s. n. (FH); Koponen 29846, 32800, 29934, 33881, 60886, 30165, 33910 (FH); Norris 64551, 63376, 63285 (FH); Brass 9385, 10942, 10956, 9699, 9698, 9870, 9389, 10024, 10942, 10956, 22621, 22543 (FH); Creek 720, 719 (FH); Clemens 11296 (FH); Sloover 42, 981 (FH); Fleischer 14 (FH); Thiers 3398, 3663, 3714 (FH); Morris 60205, 66517 (FH); Wade 8110 (FH); Weber & McVean 32214 (FH); Mundua 33 (FH); Toia 115 (FH). JAVA: Fleischer 348, 1300 (FH); Seifrig s.n. (FH); Moller s. n. (FH); Schiffner 3896, 13024 (FH). CELEBES: Everett s. n. (FH); Dixon s. n. (FH). PHILIPPINES: Copeland 827, s. n. (FH); Robinson 6596 (FH). BORNEO: Korthals s. n. (MO); Clemens 33122, 40289 (FH).

II. LEPTOCLADIELLA M. Fleisch., Musci Fl. Buitenzog 4: 1476. 1923.—TYPE: Stereodon psilura (Mitt.) M. Fleisch.

1. Leptocladiella psilura (Mitt.) M. Fleisch., Musc. Fl. Buitenzorg 4: 1205. 1923.

Sterodon psilurus Mitt., J. Proc. Linn. Soc. Suppl. Bot. 1: 112. 1859.—TYPE: India, Hooker 754 (holotype: BM; isotype: FH); Himalaya, Bahadru 1 (paratype: FH).

The costae of branch-leaves are variable within individuals. The costa can be forked or single. The other unique characters are the costal spine and the lack of central strand.

Distribution. China, the Himalayas, India, Thailand.

Additional specimens examined. NEPAL: Norkett 7559A (BM); Wallich s. n. (BM); Polunin et al. 5418a, 5421a (BM); Higuchi 18108, 16292 (HIRO). CHINA: Redfearn et al. 516 (FH, SMS, MO); Brotheros 6661 (BM). TIBET: Chen 256 (MO). INDIA: Mills et al. 754, s. n. (FH). THAILAND: Ogawa 67836 (FH).

2. Leptocladiella delicatula (Broth.) J. R. Rohrer, J. Hattori Bot. Lab. 59: 266. 1985.

Macrothamnium delicatulum Broth., Symb. Sin. 4: 131. 1929.—TYPE: China, Setschwan, Handel-Mazzetti 1486 (holotype: H).

Distribution. This species has rarely been reported or collected. The distribution of this species is restricted to southwestern China.

Additional specimens examined. TIBET: Chen 245a (MO); Zhang 467 (MO).

III. LEPTOHYMENIUM Schwaegr., Sp. Musc. Suppl. 3(1): plate 246c. 1828.—TYPE: Neckera tenue Hook.

Chiang — Phylogeny of Macrothamnium

This genus is gametophytically similar to Macrothamnium macrocarpum or M. leptohymenioides. The weak differentiation of stem- and branch-leaves can be used to distinguish the sterile specimens of Leptohymenium from those of Macrothamnium. The erect capsules are different from the inclined ones of M. macrocarpum and M. javense. Macrothamnium leptohymenioides, however, has sporophytes similar to those of M. macrocarpum, except for having cross-striate exostome ornamentation.

1. Leptohymenium tenue (Hook.) Schwaegr., Sp. Musc. Suppl. 3(1): plate 246c. 1828.

Distribution. The Himalayas, China, Indo-China, India, the Philippines, and Mexico. The geographical distribution of the species is unique. A disjunct distribution pattern has been described based on the populations of Asia and Mexico (Rohrer, 1986).

Specimens examined. BHUTAN: Kurz 89, 2525 (BM); Griffith 738, 739, 740 (BM); Sisphara 563 (BM). NEPAL: Hooker 908, 947, 955, 1169, 1840 (BM); Wailich 160, 2096, s.n. (BM); King 56 (BM, FH); Sherrin 3 (BM); Buchanan s. n. (BM); Gardner s. n. (BM); King 1894 (FH); Man 828 (FH); Kharraddiu s.n. (FH); Hara et al. 200006 (FH); Iwatsuki 1367 (FH); Mills et al. s. n. (FH); Hooker 955, 958 (FH); Baesley s. n. (FH); Rana. s. n. (FH); Higuchi 15918 (HIRO). INDIA: Hooker 951 (BM); Ryley 14 (BM); Dixon 271, 325, 609 (BM); Kurz 2261 (BM); Fleischer 3255 (FH); Griffith 738, 740, 178, s. n. (FH); Mueller 1701 (FH); Miller 11 (FH); Parish 130 (FH); Beddome 145, 563 (FH); Strachey & Winterbottom 99, 908, 953, 961, 947, 946, 955, 959, 950, 948, 958 (FH). CHINA: Redfearn, He & Su 6126, 688 (SMS). TIBET: Su 2646 (MO). BIRMA: Kurz 2820, 3344 (BM); Dixon 685 (BM); Khairuddin s. n. (FH); Dickason 7501, 7292, 7427, 9446, 9642, 9644, 9429 (FH); Svihla 3747, 3427, 9429, 3580 (FH). THAILAND: Yoda 67719 (FH); Touw 9121, 9784 (FH). PHILIPPINES: Curran et al. 16425 (FH); Clemens 9316 (FH); Jacobs 567, 14 (FH); Tan 86291 (FH). MEXICO: Sharp 5629 (FH); Norris et al. 20667 (FH); Mueller 2268 (FH); Crum 1137, 811 (FH); Arsene 7998 (FH, MO).

2. Leptohymenium hokinense Besch.—TYPE: China, Yunnan, Delvary 4131 (lectotype: BM).

Lanceolate leaves are unique to this rare species.

Distribution: Restricted to southwestern China.

Specimens examined. CHINA: Delavay 4663 (FH, BM).

IV. ORONTOBRYUM Fleisch. ex Brother. in Engler & Prantl, Nat. Pfl. ed.2, 11: 261. 1925.—TYPE: Stereodon hookeri Mitt.

1. Orontobryum hookeri (Mitt.) M. Fleisch. ex Broth. in Engler & Prantl, Nat. Pfl. ed. 2, 11: 261. 1925.

Sterodon hookeri Mitt.—TYPE: India, Hooker 819 (holotype: FH).

This species is characterized by globular capsules, monopodial growth-form, and foliose paraphyllia.

Distribution. Himalayas, India, Birma.

Additional specimens examined. HIMALAYAS: Mill et al. s. n. (FH); Iwatsuki 753 (FH); Romos 66 (BM). NEPAL: Norkett 9317 (BM); Higuchi 17494 (HIRO). INDIA: Wood 2006a, 4220c (BM); Polunin M47 (BM). BHUTAN: Griffith s. n. (BM, MO). BIRMA: Kingdon Ward 21160h (BM).

Excluded Species

Hypnum flagellaris (T. J. Kop. & D. H. Norris) T.-Y. Chiang, comb. nov.

Basionym: Leptocladiella flagellaris T. J. Kop. & D. H. Norris, Acta Bot. Fennica 131: 53-61. 1985.—TYPE: Papua New Guinea, Norris 63839 (holotype: HEL); Koponen 34317 (paratype: MO).

This species was recorded as new by Koponen and Norris (1985) from New Guinea. It is characterized by curved stem-leaves, ovate-lanceolate pseudoparaphyllia, early central strand, and well-differentiated alar cells of stem-leaves. It seems to be more related to Hypnum than it is to Leptocladiella, which is characterized by having late central strands and enlarged epidermal cells, and by lacking pseudoparaphyllia.

Additional specimens examined. NEW GUINEA: Norris 61619 (MO), Sloover 42936 (MO).

Acknowledgments. I thank Drs. Bruce Allen and Robert E. Magill for their valuable comments on taxonomic treatment. I am grateful to the curators of BM, FH, HIRO, NICH, L, MO, and PE for access to cited specimens.

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Appendix 1. Examined specimens of outgroup taxa.

Loeskeobryum cavifolium (Lac.) M. Fleisch.

Japan: Koponen 19258 (MO); Mizutani 13899 (MO); Higuchi s.n (MO).

Hylocomium splendens (Hedw.) B.S.G.

China: Redfearn & Su 745, 757b (SMS); Redferan, Allen & Wu 34625a, 34694, 34582, 35228, 35276, 35229c, 34605, 35232 (SMS); Redfearn, He & Su 1295 (SMS).

Gollania ruginosa (Mitt.) Broth.

China: Redfearn, He & Su 1035 (MO).

Leptocladiella flagellaris Norris & Koponen

New Guinea: Norris 61619 (MO); Sloover 42936 (MO).

Chiang — Phylogeny of Macrothamnium