Resurrection of the Plagiothecium longisetum Lindb. and proposal of the new species-P. angusticellum

Re-assessment of type material of Plagiotheciumnovae-seelandiae Broth. and descriptions of four new Plagiothecium taxa (Bryophyta, Plagiotheciaceae) from Australasia

A re-examination of the original collection of Plagiotheciumnovae-seelandiae described by Brotherus in 1916 indicated that this material is not homogeneous. Re-examination of the diagnosis of this species and morphological analysis supports that two separate taxa should be distinguished - Plagiotheciumnovae-seelandiaevar.novae-seelandiae and P.novae-seelandiaevar.brotherivar. nov. Also, comparisons with the original collection of Hypnumlamprostachys (= P.lamprostachys) showed differences, which supported their treatment as separate taxa. Revision of the genus Plagiothecium from Australasia (CANB, CHR, HO, MEL, WELT) and types of other species described from this part of the world (P.funale and P.lucidum) supported by the study of their diagnoses, qualitative and quantitative characteristics as well as mathematical analyses (PCA, HCA) allowed the division of the examined material into six separate groups - six separate taxa. Thereby, three distinct taxa are proposed - P.cordatumsp. nov., P.semimortuumsp. nov., and P.semimortuumvar.macquariensevar. nov. All taxa mentioned above are described in detail, their current known distribution and ecological preferences are also included. In addition, images illustrating their most important taxonomic features, as well as an original key to distinguish individual taxa are presented.

New taxa of Plagiothecium (Plagiotheciaceae) from Pakistan

A revision of specimens of Plagiothecium deposited in the herbarium of Pakistan Museum of Natural History (PMNH) collected during a Japanese lead project on Cryptogams in the Western Himalaya (Pakistan) shows that the material consists of five taxa. Of the studied samples, the most common taxa were from the P.denticulatum complex, including Plagiotheciumdenticulatumvar.obtusifolium, new to Pakistan. Examination of the rest of the collection showed that it consists of specimens with a unique combination of qualitative and quantitative characteristics of their gametophyte. For example, for small plants, with small asymmetrical, folded leaves, gradually tapering into long, acuminate, not denticulate apex, whose leaf cells are long and narrow, making the cell areolation tight, the name Plagiotheciumfilifolium is proposed. For other plants with large leaves, loosely arranged on the stem, concave, symmetrical to slightly asymmetrical, with denticulate apex and long decurrency composed of rectangular and spherical, inflated cells, the name Plagiotheciumhiguchii is proposed. However, within this material, specimens differ in terms of the length and width of the leaf cells and therefore, within this taxon, two varieties are distinguished: Plagiotheciumhiguchiivar.higuchii and Plagiotheciumhiguchiivar.brevicellum.

Taxonomic revision of the Plagiothecium curvifolium complex

Supported by the examination of specimens from the entire range and by the analysis of type specimens and the diagnosis of individual names, morphological and genetic studies of the Plagiothecium curvifolium complex resulted in the conclusion that this taxon should be recognized as four separate taxa. In addition to P. curvifolium s.str., there is a variety that is proposed as a new combination–P. curvifolium var. recurvum; resurrection of the forgotten P. decursivifolium; and the description of a new species–P. imbricatum. The features that distinguish individual taxa focus primarily on: plant size; arrangement of leaves on the stem; the symmetry, dimensions, shape, concavity and folding of leaves; cell length; serration of the leaf apex; the shape of the decurrencies; the length of the sporophyte and the shape of the operculum. For all described taxa, the distribution, ecological preferences, key to their identification and detailed photographic documentation have been provided.

Revision of the Original Material of Plagiothecium denticulatum var. obtusifolium (Turn.) Moore and New Synonyms for This Taxon

Hypnum denticulatum var. obtusifolium was described by Turner in the early nineteenth century. This taxon, now known as Plagiothecium denticulatum var. obtusifolium, has not been studied in detail or received a detailed description. During the revision in the Natural History Museum (herbarium BM), a specimen described there as a type (BM000890810) was found, but a careful analysis showed that it is currently not a type specimen. On the other hand, the conducted research showed that the holotype of this taxon is the figure attached by Turner to the newly described taxon. However, because the holotype does not contain all taxonomically significant features, the specimen found was used to designate the epitype of this name (BM000890810). Therefore, this paper provides the first complete description of the qualitative and quantitative characteristics of this taxon, which is today known as P. denticulatum var. obtusifolium. Forty qualitative and quantitative characteristics analyzed made it possible to make redescription of the examined taxon. Moreover, analysis of two morphologically similar, currently distinct taxa, P. sandbergii and P. denticulatum var. auritum, revealed no differences between them. Therefore, these taxa were proposed as new synonyms of P. denticulatum var. obtusifolium. Additionally, for both taxa mentioned above, lectotypes were proposed for P. denticulatum var. auritum, specimen PC0132639, and for P. sandbergii, specimen PC0132604, both from the Muséum National d’Histoire Naturelle, Paris, France (Herbarium PC).

Plagiotheciumtalbotii, a new species from the Aleutian Islands (Alaska, U.S.A.)

Plagiotheciumtalbotii sp. nov. is described from Attu Island, Alaska, U.S.A. The newly-described species is not similar in appearance to any Northern Hemisphere species; only the habit is similar to P.platyphyllum. However, it not only occupies a different habitat than that species, but genetically and morphologically, it is clearly distinct from it. The results of DNA sequencing, a detailed description of the morphological features, illustrations, ecological preferences and currently known geographical distribution of P.talbotii are presented. The most important distinguishing morphological features of this species are: the size of the plant; dimensions and symmetry of the leaves; dimensions of cells and their areolation; entire leaf apex; and long decurrencies with some inflated cells. Additionally, we propose to place P.talbotii in section Plagiothecium, which is confirmed by genetic analysis and morphological features.

Plagiotheciumschofieldii, a new species from the Aleutian Islands (Alaska, USA)

Plagiotheciumschofieldii sp. nov. is described from the Aleutian Islands, Alaska, U.S.A. Some morphological features of this species correspond to P.lamprostachys (Southern Hemisphere species); however, Plagiotheciumschofieldii is genetically and morphologically different from this and other common Northern Hemisphere species e.g., P.denticulatum, P.platyphyllum, or P.ruthei. The most important distinguishing morphological features differentiating this species are: the arrangement of the leaves on the stem; dimensions, concavity and symmetry of the leaves; dimensions of cells and their areolation; orientation of capsules. Additionally, due to the strong concavity of the leaves, they are very often badly damaged under the microscope. We present the results of DNA research of the analyzed samples, and a detailed description of the morphological features. The new species is illustrated, and its ecological preferences and currently known geographical distribution are presented. Additionally, the authors propose to add this species to Plagiothecium section, which is confirmed by morphological features and genetic analysis.

The Genus Plagiothecium Schimp. (Plagiotheciaceae, Bryophyta) in Eurasia: An Annotated Checklist with Distribution and Ecological Data

An annotated checklist of the pleurocarpous moss genus Plagiothecium in Eurasia is presented for the first time based on a thorough review of the literature. Data have been compiled from previous relevant works conducted on the genus over more than 70 years and published up to the end of June 2020 for 107 Eurasian countries (and islands). Sectional classification is based on molecular phylogeny of the genus published recently. A total of 41 taxa are reported, including 29 species and 12 infraspecific taxa (nine varieties and three forms) belonging to eight sections. The highest numbers of taxa were found in China (20 taxa), the Russian Federation (20 taxa) and Japan (18 taxa), while the smallest numbers of taxa were recorded in the Middle East, Central Asia and the islands area. Not a single species of Plagiothecium was recorded in 26 regions, whereas P. denticulatum, P. nemorale and P. cavifolium turned out to be the most widespread species in the entire study area. They were recorded in most of the surveyed countries and islands. For each accepted taxon, information on relevant literature, synonyms, distribution within Eurasia and globally are provided. Comments on each taxon, ecological preferences, and notes on doubtful records are also included. Additionally, distribution maps for each recognised taxon are supplied. This checklist can enlighten and foster a better understanding of the distribution, diversity, and ecology of Plagiothecium in Eurasia and provides an incentive for future research on the genus.

A new synonym from Hawaii and lectotypification of Plagiothecium longisetum (Plagiotheciaceae)

Plagiothecium mauiense was first described in 1927 by V.F. Brotherus, based on materials from Hawaii. It has, so far been, treated as a separate species. A detailed analysis of the original material housed in the New York Botanical Garden Herbarium (NY01256708) found the specimen to be characterised by a lack of metallic lustre; concave, asymmetrical, lanceolate to lanceolate-ovate leaves, shrunken in their dry condition; a straight, not denticulate, acute to apiculate apex; elongate-hexagonal cells in irregular transverse rows, 101-131 × 15-21 µm at mid-leaf; very lax areolation, with decurrencies composed of three rows of cells. These characteristics indicate that this species is identical to the original material of P. longisetum (e.g. H-SOL 1563 011; PC0132572). Hence, we propose that P. mauiense should be recognised as a new synonym of P. longisetum. In addition, a review of P. longisetum syntypes found one (H-SOL 1563 011) to have the same date of collection as the protologue, and to possess a quite abundant gametophyte turf with well-preserved sporophytes, indicating it to be fertile. Considering the above, we propose that specimen H-SOL 1563 011 be designated the lectotype of P. longisetum.

Lectotypification of the name Stereodon nemoralis Mitt. (Plagiotheciaceae), a basionym of Plagiothecium nemorale (Mitt.) A. Jaeger

In 1859, William Mitten described Stereodon nemoralis (≡ Plagiothecium nemorale) based on the gathering of Sir J.D. Hooker from India. However, the protologue did not indicate any specific specimen or illustration. For the past 50 years, the original material (NY 913349) deposited at the NY Herbarium has been considered as the holotype. However, this assumption has since been found to be incorrect, because in the Herbarium of The Natural History Museum exists other original material of this species (BM 1030713), collected by Hooker. In addition, the specimen from NY Herbarium is in poor condition and its most important diagnostic characters are not visible. In contrast, the material from BM Herbarium is in very good condition, and therefore it is herein designated as the lectotype. Also, the paper describes the resolution of this type, a process complicated by changes that had occurred in the provisions of subsequent botanical Codes.