Orthotrichum alpestre, a New Addition to the Moss Flora of Poland, with Notes on O. schimperi (Orthotrichaceae: Bryophyta)

The occurrence of two epiphytic moss species, Orthotrichum alpestre Bruch & Schimp. and O. schimperi Hammar, in the moss flora of Poland is discussed. The former represents an entirely new country record based on a specimen collected from the Polish Eastern Carpathians, whereas the latter is reinstated as a member of the Polish moss flora. The complex and entangled taxonomic and nomenclatural history of O. schimperi is outlined, sources of its confusion are discussed, and two correctly determined specimens from Poland are cited. The two species are briefly characterized and illustrated, and a key to the genera and species of Polish orthotrichaceous mosses is presented.


Introduction
Orthotrichum Hedw. is one of the most distinctive of all moss genera, which is at a glance distinguished by its immersed to short-exserted capsules that are most often ribbed and only seldomly smooth with large campanulate-mitrate and usually hairy calyptrae covering the entire capsule. Plants lacking sporophytes are recognized by their orthotropic, sympodially branched stems and small, isodiametric, and mostly papillose laminal cells with incrassate walls. These xerophytic adaptations are associated with the ecological preferences of the species of Orthotrichum, which generally grow in dry, sunny habitats, either as epiphytes on the bark of deciduous trees or shrubs, or epipetrically on rocks, boulders, or stone walls.
Twenty species of the broadly interpreted genus Orthotrichum have been recorded from Poland in the latest catalog of Polish mosses (Ochyra et al., 2003). A subsequent reexamination of the herbarium specimen showed that O. microcarpum De Not. was erroneously reported from Poland because the voucher specimen collected by A. Żmuda in 1910 proved to be O. pallens Brid. ). Accordingly, this species was excluded from the moss flora of Poland. However, this loss was compensated by O. shawii Schimp., whose record from Poland was resurrected from obsolescence. This species was found in the second half of the nineteenth century near Barwice in northwestern Poland by Ruthe (1873), but the record has been generally overlooked. This species has not been rediscovered in Poland, yet Ruthe's record is confirmed by the voucher specimens deposited in BM and TR .

Methods
The two species of Orthotrichum that are considered to be new records to the moss flora of Poland were found during a revision of the herbarium holdings of the genus in the bryological herbarium in the W. Szafer Institute of Botany, Polish Academy of Sciences (KRAM).

Remarks
Orthotrichum alpestre is a small to medium-sized moss that has strongly papillose leaves, which can provide a glaucous tinge to the plants ( Figure 1A). The papillae of the leaf cells are more or less prominent and commonly forked ( Figure 1B). The capsules are 1/2-3/4 emergent, with an urn obloid-ovoid when mature. The peristome is double, formed by eight pairs of the exostome teeth and eight endostome segments ( Figure 1C). The outer peristome layer (OPL) ornamentation of the exostome teeth is formed by dense papillae below and a mixture of papillae and distinct striae above ( Figure 1D). The calyptra is covered with usually scattered, stout papillose hairs ( Figure 1A,C).
The voucher material of this species was originally determined by the collector J. Żarnowiec as Orthotrichum pumilum and its duplicate was deposited in the bryophyte collection at KRAM. It was subsequentlly published under this name in a paper dealing with the mosses of the Terebowiec stream valley (Żarnowiec, 2010) and, secondarily, this record is cited in a monograph of the moss flora of the Western Bieszczady Mountains (Żarnowiec & Stebel, 2014 The two aforementioned specimens of Orthotrichum schimperi were originally determined by A. Stebel as Orthotrichum pumilum and their duplicates were donated to the bryophyte herbarium at KRAM. The first of these from Węgorzewko in the Pojezierze Mazurskie was published under this name by Stebel (1997), whereas the second specimen from the Świętokrzyski National Park was published by Paciorek et al. (2016) and it is also cited in the unpublished doctoral thesis of its collector (Paciorek, 2017).

Remarks
Orthotrichum schimperi is a small epiphytic moss. The plants are green-colored above and brownish below. The leaves are erect and loosely-appressed when dry, ovate-oblong to oblong-lanceolate. The capsules are immersed to shortly emergent ( Figure 2A,C), ovoid or pyriform when moist, abruptly contracted into the seta. The stomata are immersed, scarcely covered by the guide cells. The peristome is double, formed by eight pairs of the reflexed exostome teeth and eight endostome segments with a conspicuously broad base, 1/2-3/4 as long as the exostome teeth ( Figure 2C,D). The calyptra is naked ( Figure 2B).

Discussion
Orthotrichum alpestre is a subarctic-subalpine species. In Europe, it is most often found in the subalpine or alpine zones (Martínez-Abaigar et al., 1995), and outside Europe, it is known from North America and Southeast and Central Asia.
Orthotrichum alpestre is morphologically similar to O. stramineum, but it can be distinguished mainly by having (i) tall and commonly forked papillae of the laminal  Figure 1B), whereas the latter species usually has shorter and only rarely branched papillae of the laminal cells; (ii) an OPL that is densely papillose below and striate-papillose above ( Figure 1D), whereas the exostome teeth in O. stramineum are uniformly papillose on the outer side, and the ornamentation of the upper part does not contrast with that of the lower part; (iii) a short capsule neck, mostly shorter than the urn, whereas in O. stramineum the neck is long, commonly as long as the urn, and gradually tapered to the seta; and (iv) a naked or sparsely haired vaginula with a few variable hairs, whereas in O. stramineum, the vaginula is covered with long papillose hairs (cf. Blockeel & Lara, 2015).

cells (
Orthotrichum schimperi is a member of a difficult and critical complex of species centered around O. pumilum, which also includes O. pallens and O. philibertii Venturi. The most important difference between O. schimperi and O. pumilum is in the shape of the capsule (cf. Blockeel, 2019). It is narrowly ovoid, widest at the middle, and somewhat constricted below the mouth in O. schimperi (Figure 2A,C) and its base is abruptly contracted to the seta. In contrast, O. pumilum has slightly longer and narrower capsules ( Figure 2E), which gradually taper at the base into the seta. There are also differences in the details of the peristome between these two species. In O. schimperi, the endostome segments are shorter, 1/2-3/4 as long as the exostome teeth, and conspicuously broad at the base ( Figure 2D). In O. pumilum, the segments are long and narrow, almost as tall as the exostome teeth ( Figure 2F), and not or only slightly widened at the base.
Orthotrichum pumilum was one of the earliest recognized species of the genus and was described in 1799 from the material collected in Sweden, and its prestarting point name was validated by an anonymous author of a review of Swartz's (1799) work published on June 1, 1801 in The Monthly Review (Anonymous, 1801). The species was subsequently accepted by Dickson (1801) in his treatment of the cryptogams of the British Isles, which was published on October 4, 1801 (Sayre, 1959). He provided a short description of the species in Latin, cited one specimen from Ireland, and gave a full reference to Swartz's (1799) original description of the species whose name was then already validly published. Interestingly, some authors (e.g., Grout, 1935;Limpricht, 1890;Wilson, 1855) considered O. pumilum sensu Dickson as a validly published name, and in Index muscorum (Wijk et al., 1964(Wijk et al., , 1969, it was considered as an illegitimate homonym of O. pumilum Sw. The latter species was accepted in most floras and taxonomic treatments published in the first four decades of the nineteenth century, both in the British Isles (e.g., Smith, 1804;Turner, 1804) and continental Europe (e.g., Bridel, 1826Bridel, -1827Hübener, 1833;Schwaegrichen, 1816).
The real confusion regarding the taxonomic interpretation of Orthotrichum pumilum was introduced in Bryologia europaea (Bruch et al., 1837) because of an incorrect application of the name of this species. The authors of this opus, which was then considered to be the oracle of taxonomic and nomenclatural matters regarding European mosses, disregarded the principle of priority and ascribed the name O. pumilum to Schwaegrichen (1816), although this author did not describe a new species because he gave in his treatment full reference to O. pumilum sensu Swartz and in this way included the type of this species name in his O. pumilum. Thus, although the description and elegant, colorful plate represented a different species in Schwaegrichen (1816), Bruch and Schimper, the authors of the text and the taxonomic concept in Bryologia europaea, should have introduced a new name for this species and not adopt a name, which was used for a different and accepted species.
This already complicated situation was additionally aggravated by the fact that the authors of Bryologia europaea accepted Orthotrichum pumilum sensu Swartz but completely broke the principle of priority by accepting O. fallax Brid., which was described by Bridel (1826Bridel ( -1827 (1869) and Limpricht (1876), in two major floras related to Silesia. Later, Limpricht (1890) changed his mind and accepted O. schimperi as a species in its own right, as did other authors, for example, Philibert (1891), Roth (1904), andBrotherus (1923).
Orthotrichum schimperi is a Holarctic species that has its main center of distribution in Europe, with some isolated occurrences in California in North America and Central Asia (Lara & Garilleti, 2014). It is rather common in the Mediterranean region where it extends to North Africa (Morocco, Algeria, Tunisia, Libya) and Turkey in the Near East (Ros et al., 2013), but in Central Europe, its geographical range is not well known, because it was not distinguished from the closely related O. pumilum. The species is absent from much of eastern Europe and is unknown from Russia and in the north extends to southwestern Finland (Hinneri, 1976) and southern Sweden and Norway (Hallingbäck et al., 2008). It is very rare and widely scattered in Britain, including southeastern Wales, southeastern England, and eastern Scotland (Blockeel, 2019).
Orthotrichum schimperi was mentioned from Poland in the old literature under this name but usually without citation of any specimens (Limpricht, 1876(Limpricht, , 1890 or as O. fallax Schimp. non Brid. (Chałubiński, 1886;Krupa, 1878). A revision of these historical collections deposited in KRAM revealed that they all correctly represented O. pumilum. Likewise, the specimens of O. schimperi collected in Głogoczów in the Pogórze Wielickie in the Polish Western Carpathians were distributed in Bryotheca Polonica as No. 21 (Żmuda, 1911). The specimens in KRAM (B-001470 and B-171928) consist of O. pumilum Sw. mixed with Nyholmiella obtusifolia.
Following the generally accepted tendency to consider Orthotrichum schimperi to be conspecific with O. pumilum, the species has not been accepted in the recent checklists of the mosses in Poland (Ochyra & Szmajda, 1978;Ochyra et al., 2003). However, this species was previously included by Szafran (1961) in the moss flora of Poland, but the description of this species and a key to the determination of Orthotrichum species are highly confusing and misleading in this work. This author used the presence and abundance of gemmae as the only character distinguishing O. schimperi from O. pumilum in a key to species of this genus and stated (Szafran, 1961, p. 22) that the axillary gemmae occur in profusion in O. schimperi, whereas in O. pumilum, they are absent or very rare (only 1-3 per stem). The selection of this character is unfortunate and confusing because, apart from some species of the orthotrichalean mosses that regularly and abundantly produce gemmae, including Nyholmiella obtusifolia, N. gymnostoma, Pulvigera lyellii, gemmiferous plants are only occasionally known in a number of Orthotrichum species, especially in the older stage of ontogenesis (cf. Plášek et al., 2007), and they have no taxonomic value. The presence versus absence of the gemmae in O. schimperi and O. pumilum cannot be considered a reliable distinguishing character because it appears that the occurrence of the gemmae varies markedly in the former species. In the plants from Poland and other regions in Central Europe, they occur sparingly as already noted by Limpricht (1890, p. 77) or are even missing, whereas they occur commonly in the plants from the Iberian Peninsula (Lara & Garilleti, 2014, p. 119). Szafran (1961, pp. 34-35) introduced essential confusion in the description of the peristomes for the species in question. According to this author, Orthotrichum pumilum has an ovoid capsule with endostome segments that are conspicuously wide at the base. However, this shape of the capsules and the endostome segments is typical of O. schimperi. According to Szafran (1961, p. 34), O. schimperi has segments of the endostome as long as the exostome teeth, but actually, such segments occur in O. pumilum. Additionally, the calyptra is glabrous in O. pumilum, whereas Szafran (1961) stated that sometimes it is covered with scattered short hairs. Considering these inaccuracies in the treatment of the species, it was not possible to correctly identify them following the work of Szafran (1961); in fact, O. schimperi has not been recorded in the Polish bryological literature in the last half-century.
The true distribution of O. schimperi in Poland can be established only after a revision of the holdings of this complex in all Polish and foreign (especially German) herbaria. As mentioned above, most specimens cited as Orthotrichum schimperi from Poland proved to be mis-determinations; thus, it is likely that the specimens reported in the present account are the only true specimens of this species cited hitherto in the Polish literature. In the largest bryophyte herbarium in Poland at KRAM, approximately 170 specimens of O. pumilum are deposited and only two out of this number belong to O. schimperi, which means that the ratio of occurrence of O. schimperi and O. pumilum collected in Poland was approximately 1-2:100. It is difficult to expect that this ratio will be significantly different in other herbaria, especially if a similar proportion was also observed by the first author in the Czech herbaria. If this is confirmed by a revision of the holdings in other herbaria, O. schimperi may turn out to be a rare or very rare species in Poland, and this would not be surprising considering its clear Mediterranean affinities.

Key to Genera and Species of Orthotrichaceous Mosses in Poland
The revolutionary taxonomic and classificational changes in the orthotrichalean mosses in recent decades, as well as a number of new additions to the moss flora of Poland, prompted the authors to compile a new key to the determination of the genera and species, which has traditionally been classified for the genera Orthotrichum and Ulota. In the future, the Polish material of Ulota needs revision to confirm recent taxonomic changes in the U. crispa (Hedw.) Brid. complex (Caparrós et al., 2016). However, two species of Orthotrichum, O. stellatum and O. moravicum, have been included because they are known from the coterminous countries, and they are very likely to also be discovered in Poland -The latter species has been described only recently from the Czech Republic , and its global distribution is still poorly known. Both are marked with an asterisk (*) in the key. The seventh genus of the Orthotrichaceae, Zygodon Hook. & Taylor, which consists of five species in Poland, is not included in the following key, and its species are keyed by Stebel and Żarnowiec (2017).