Orthotrichaceae Arn.

Elements in the following description are taken from Vitt (1994).

Plants small to robust, mostly dull, forming dark green, red-brown, green-brown, or yellow-green tufts, cushions, or mats on bark or rock. Stems erect and often forked or creeping and giving rise to numerous erect, simple, or forked branches, in cross-section lacking a central strand. Leaves crowded, erect-spreading to squarrose-recurved when moist, erect, spirally twisted, crisped, or flexuose when dry, sometimes undulate or rugose, ± keeled, lingulate, ovate-lanceolate, or linear-lanceolate, at apex acute, rounded-obtuse, or occasionally acuminate, apiculate, or hair-pointed; margins plane to revolute or rarely incurved; upper laminal cells mostly rounded-hexagonal, rarely elongate, thick-walled, usually papillose but less often smooth, unistratose to multistratose; marginal cells rarely differentiated by shape but often bistratose; basal cells linear, subquadrate, rectangular, sometimes pigmented, smooth, bulging, papillose, prorate, or tuberculate; alar cells rarely differentiated. Costa single and strong, ending near the apex or excurrent. Gemmae occasional, either in leaf axils, on abaxial surface of lamina or on an excurrent extension of the costa. Paraphyllia absent.

Sexuality variable. Perichaetia terminal on branches or stems; perichaetial leaves sometimes enlarged. Perigonia gemmiform, terminal or lateral, sometimes produced by dwarf male plants. Setae very short to elongate, mostly smooth, rarely papillose; capsules immersed to exserted, erect and symmetric, broadly ovoid to narrowly cylindric, sometimes 8- or 16-ribbed; mouth transverse, often constricted when dry; exothecial cells rectangular, mostly firm- or thick-walled, often differentiated in bands; stomata 2-celled, immersed or superficial, restricted to neck or occurring over urn; annulus none or variably developed; operculum mostly rostrate. Peristome double, single, rudimentary, or absent; exostome teeth 16 but usually united in pairs, erect or reflexed when dry, thick, ± lanceolate, densely papillose or striate, sometimes with adherent preperistome fragments, often reduced to a low membrane; endostome variable and sometimes absent, with 0, 8, or 16 narrow and hyaline segments arising from a low membrane; cilia none. Preperistome occasionally present. Calyptra mostly mitrate, sometimes cucullate, usually covering most of the capsule, often plicate, smooth or papillose, hairy to naked. Spores 1- or occasionally many-celled, sometimes variable in size, finely to coarsely papillose.

Vitt (1994, p. 591), who has revised several of the New Zealand (N.Z.) genera, provided these summary comments on the family in his treatment for the Flora of Mexico: "The Orthotrichaceae are diplolepideous in peristome structure. The outer plates of the exostome teeth are thicker than the inner. The endostome segments are linear and hyaline, free at the base and alternate with or opposite to the teeth. The capsules are erect, often ribbed, and generally short-stalked. The perichaetia are terminal. The leaves have mostly thick-walled, rounded-hexagonal upper cells that are commonly bulging or papillose. The alar cells are rarely differentiated. The calyptrae are mitrate (except Drummondia, Zygodon, and Amphidium). The plants are mostly xerophytes, growing on bark or rock surfaces." His Mexican treatment provides an overview of the family, although there is little overlap at the species level with the N.Z. flora.

The Orthotrichaceae are one of the largest and most diverse of moss families, with up to 27 genera and perhaps as many as 600 species worldwide. The family is cosmopolitan in distribution, but most diverse in tropical and temperate regions. The plants are xerophytes and mostly grow on bark or on rock.

The Orthotrichaceae have attracted a great deal of systematic and taxonomic attention in recent years. Some intra-familial relationships remain inadequately resolved, although molecular methods have contributed to a clearer understanding of these. Goffinet & Vitt (1998, p.146 et seq.) presented a classification of the Orthotrichaceae based on morphological characters and molecular (chloroplast rbcL) sequences in which they restricted the family to 20 genera distributed between two subfamilies (Orthotrichoideae and Macromitrioideae) each with two tribes.

Subfamily Orthotrichoideae

Tribe Zygodonteae with seven genera including Zygodon Hook. & Taylor and Leratia Broth. & Paris, as well as two genera not accepted here (Codonoblepharon Schwägr. and Bryomaltaea Goffinet)

Tribe Orthotrichaeae with five genera including Ulota Mohr and Orthotrichum Hedw. (incorporating Muelleriella Dusén)

Subfamily Macromitrioideae

Tribe Schlotheimieae with one genus, Schlotheimia Brid.

Tribe Macromitrieae with nine genera, including Macromitrium Brid. and Macrocoma (Müll.Hal.) Grout.

While the concepts of the larger genera in the Orthotrichaceae have remained relatively stable in recent years, several smaller genera have either been recently proposed or resurrected after many decades or more of disuse, with some being segregates of much larger genera. Many of these changes have involved taxa placed by Goffinet & Vitt (1998) in the subfamily Orthotrichoideae, particularly the tribe Zygodonteae. The proposed changes have relied on data from both reassessments of morphological features and molecular data, and many of these proposed taxonomic modifications have involved species occurring in N.Z. Some of the proposed changes seem strongly supported by data, while others seem to have been made prematurely or to make little sense viewed in a N.Z. context.

Among recent changes relevant to the N.Z. flora:

Goffinet & Vitt (1998) transferred the N.Z. endemic species Bryodixonia perichaetialis Sainsbury to Ulota as Ulota perichaetialis (Sainsbury) Goffinet in Goffinet & Vitt. This transfer is supported by both molecular and morphological data and is followed here.

Goffinet et al. (2004) proposed the inclusion of the species traditionally (Brotherus 1925) placed in Muelleriella Dusén within Orthotrichum. This synonymy is strongly supported by molecular data and is followed here.

Goffinet & Vitt (1998) proposed the resurrection of the genus Codonoblepharon Schwägr. for two species of Zygodon with smooth laminal cells. The two species they considered to belong to Codonoblepharon were Zygodon menziesii (Schwägr.) Arn. (with a N.Z. type) and Z. pungens Müll.Hal. (with a Venezuelan type). Goffinet et al. (2004) subsequently made the combination C. forsteri (With.) Goffinet in Goffinet & Vitt for a European species. Matcham & O'Shea (2005) subsequently proposed combinations in Codonoblepharon for several additional species of Zygodon, including two occurring in N.Z. In a N.Z. context this expanded concept of Codonoblepharon is not wholly convincing and a conservative approach is taken here: Zygodon menziesii and its purported allies are retained in the genus Zygodon, as proposed by Lewinsky (1990).

Goffinet & Vitt (1998) also suggested the creation of a monotypic genus Bryomaltaea Goffinet in Goffinet & Vitt for the widespread Zygodon obtusifolius Hook. (with a N.Z. type). Goffinet et al. (2004) subsequently suggested, primarily on the basis of molecular data, that Z. obtusifolius Hook. be incorporated within an expanded concept of the genus Leratia Broth. & Paris, typified by Leratia neocaledonica. The transfer of Z. obtusifolius to the genus Leratia is accepted here.

Plášek et al. (2015) proposed the creation of a monotypic genus Plenogemma Plášek, Sawicki, & Ochyra to accommodate the dioicous, gemmae-producing, and essentially northern hemisphere Ulota phyllantha Brid. (which in the N.Z. region occurs only on Macquarie I.). The transfer of U. phyllantha to this newly described genus is not accepted here.

Thus, seven genera of Orthotrichaceae (Leratia, Macrocoma, Macromitrium, Orthotrichum, Schlotheimia, Ulota, and Zygodon) are discussed here as part of the N.Z flora. Amphidium, which was treated in this family by Sainsbury (1955), is treated in the Rhabdoweisiaceae.