Marsupella subemarginata (Gymnomitriaceae, Marchantiophyta) Newly Found in the Carpathians in the Polish and Slovak Tatras

Marsupella subemarginata Bakalin & Fedosov is a semi-cryptic Eurasian species. Recently, it has been found in the Far East (Kamchatka and Japan) and Swiss Alps, as well as the Giant Mountains (Sudetes, Czech Republic). e plant was also observed in the Carpathians for the first time. A revision of the herbarium collections of M. emarginata (Ehrh.) Dumort. consisting of 102 specimens from the Polish and Slovak Tatra Mountains revealed the occurrence of M. subemarginata at 24 localities, eight of which were in the Polish Tatras. Most of the localities of this species were concentrated in the High Tatras, and only four sites were discovered in the Western Tatras. Marsupella subemarginata has been briefly characterized morphologically and illustrated. e habitat requirements of the species have been described in detail, and the floristic composition of its phytocoenoses has been shown in a phytosociological table consisting of 10 relevés. Marsupella subemarginata is a valuable addition to the liverwort flora of Poland and Slovakia, which currently consist of 241 and 232 species, respectively. Currently, the liverwort flora of the Tatras comprises 195 species, including 185 species in Poland and 186 species in Slovakia.


Introduction
Currently, there are 194 species of liverworts in the Tatra Mountains (Mts), which are the highest range in the Carpathians (Górski & Váňa, 2014). e history of research on this group of plants in the Tatra Mts dates back over 200 years. It began with a comprehensive study Flora Carpathorum Principalium… (Wahlenberg, 1814). e list of species growing in these mountains can be considered almost complete, although the data on the distribution or threats to various liverworts need to be supplemented (Górski, 2020). Since 2000, only two unreported species have been identified in the entire Tatra Mts: Gymnomitrion adustum Nees and Nardia compressa (Hook.) Gray (Górski, 2010;Górski & Váňa, 2011). All the other additions to the flora have been mountain liverworts, which were not found in the Polish Tatras or in Poland, but instead found only in the Slovak Tatras: Cephaloziella massalongii (Spruce) Müll. Frib.; C. varians (Gottsche) Steph.; Jungermannia borealis Damsh. & Váňa; and J. exsertifolia Steph. subsp. cordifolia (Dumort.) Váňa (Górski & Váňa in Ellis, Asthana et al., 2013;Klama in Ellis et al., 2011;Váňa & Górski in Ellis, Bakalin, et al., 2013;. Some species were identified for the first time in the Slovak Tatras, for example, Neoorthocaulis binsteadii L. Söderstr., De Roo & Hedd. (Górski in Ellis et al., 2012). All the plants listed above are morphologically well-defined taxa, which do not raise any doubts about their taxonomic status. ey were found only recently since most of these species are rare (though not all of them), and because in recent years, scientists have intensified hepaticological research in the Tatra Mts. In recent years, scientist have also been conducting intense molecular research on bryophytes. Cryptic species of bryophytes are particularly interesting. First, they are usually detected using genetic or biochemical methods, and then their morphological diagnostic traits are recognized, e.g., in the Conocephalum conicum complex (Szweykowski et al., 2005). is was also the case with Marsupella emarginata (Ehrh.) Dumort., from which a new species, Marsupella subemarginata Bakalin & Fedosov (Bakalin et al., 2019), was distinguished and described. is new species is distributed in both amphi-Pacific and amphi-Atlantic areas, and its localities were found in the Kamchatka Territory (Russia), Honshu (Japan), and Canton de Valais (Switzerland) (Bakalin et al., 2019). Soon aer the new species had been described, another European locality was found in the Giant Mts (Czech Republic) (Kučera in Ellis et al., 2021).
e presence of M. subemarginata in two vast European mountain ranges (the Alps and the Sudeten) suggests that this plant might also be found in the Carpathians. e author of this study decided to investigate this hypothesis using the rich herbarium material from the High Tatras and Western Tatras in Poland and Slovakia. e material represented all altitude levels of this mountain range and its diverse microhabitats. Marsupella emarginata is a common species in the Tatras. It was first found there in the second half of the nineteenth century (Hazslinszky, 1885;Krupa, 1878Krupa, , 1882Krupa, , 1888Limpricht, 1877aLimpricht, , 1877bSzyszyłowicz, 1884). Currently, this plant has been found in 228 localities recorded in 37 publications (they are listed by Górski & Váňa, 2014; see also Górski, 2015Górski, , 2016. Most of the localities were found in the High Tatras in Slovakia (120 sites). is liverwort is a multizonal mountain species that can be found in the Tatras at altitudes of 800-2,633 m a.s.l. (Duda & Váňa, 1981;Szyszyłowicz, 1884). It occurs in damp or wet habitats, where it grows on stones in streams, or on rocks sprinkled with dripping water. Marsupella emarginata can also grow completely submerged. is article presents the results of the revision of the herbarium holdings of the broadly conceived M. emarginata. e author confirmed the presence of M. subemarginata in the Carpathians.

Herbarium Data
e original material consisted of 102 specimens named M. emarginata, which were collected in the Polish and Slovak Tatras between 2003 and 2020 and deposited in the herbarium of the Poznań University of Life Sciences, Poland (POZNB). e revised material represents nearly 45% of all known localities of M. emarginata in the Tatra Mts. In total, there are 228 localities (see Górski, 2015Górski, , 2016Górski & Váňa, 2014). e identification of the newly described species M. subemarginata was based on the following two traits indicated by Bakalin et al. (2019): the thickness of cell walls in the hyaloderm layer as seen in a cross-section of the stem and the size of mid-leaf cells. Other differences, i.e., the color of the plants and their size, were used only as auxiliary criteria for identification of the species. e research material came only from the herbarium; therefore, it was not possible to observe oil bodies. e locations of all M. subemarginata sites were shown in a Military Grid Reference System (MGRS) sized 1 km × 1 km (e.g., 34UDV2752; see Specimens Examined).

Description of the Study Area
e Tatra Mts are the highest mountain ridge in the Carpathians (Figure 1). ey are a part of the Central Western Carpathians. e Tatra Mts ridge is 80 km long (56.5 km in a straight line) and has a maximum width of 18.5 km (15 km on average). e ridge forms a border separating Poland and Slovakia. e area covers 785 km 2 , including 610 km 2 (77.7%) in Slovakia and 175 km 2 (22.3%) in Poland (Radwańska-Paryska & Paryski, 2004). e massif is divided into the Belianske Tatry Mts ("a" in Figure 1A), the High Tatra Mts (Tatry Wysokie and Vysoké Tatry; "b" and "c" in Figure 1A and Figure 1C,D), and the Western Tatra Mts (Tatry Zachodnie and Západné Tatry Mts; "d" and "e" in Figure 1A and Figure 1E,F). e Belianske Tatry Mts are located entirely in Slovakia. ey cover an area of 67.5 km 2 , and their main ridge is~13 km long. ey consist entirely of sedimentary rocks, mostly limestone, marl, and dolomite. e highest peak is Havran (2,152 m a.s.l.). e High Tatra Mts cover an area of 335 km 2 . ey are the highest mountain range with Mt Gerlachovský štít (Gerlach; 2,655 m a.s.l.) being the highest peak in the Carpathians. In this part of the massif, in Slovakia, the next highest peaks of the Tatra Mts are Mt Lomnický štít (Łomnica; 2,634 m a.s.l.), Mt Ladový štít (Lodowy Szczyt; 2,627 m a.s.l.), and Mt Pyšný štít (Durny Szczyt; 2,623 m a.s.l.). On the Polish side, on the borderline ridge, the highest peak is Mt Rysy (2,499 m a.s.l.), which is the highest peak in Poland. Most of the High Tatra Mts, 253 km 2 , is located in Slovakia (Nyka, 2000). e length of the ridge is 16.5 km (Radwańska-Paryska & Paryski, 2004). e High Tatra Mts are built mostly of a crystalline core of granitoid with little sedimentary rock.
e average annual temperature in the vertical profile of the Tatra Mts ranges from +8°C to <−2°C, a difference of approximately 0.5°C per 100 m (Łupikasza & Szypuła, 2019). e spatial layout of the vegetation is associated with changes in temperature (accounting for 2°C). e upper limit of the lower mountain belt corresponds to an isotherm of +4°C, the upper limit of the upper mountain belt to +2°C, that of dwarf mountain pines to 0°C, and the alpine belt to −2°C (Hess, 1996).

Discussion
Marsupella subemarginata is a semi-cryptic species distinguished from M. emarginata. Bakalin et al. (2019, p. 65), who provided the diagnostic characteristics of the new species, stressed the fact that there were minor morphological differences and that their stability was uncertain. e most important traits of M. subemarginata that distinguish it from M. emarginata are the thickened cell walls of the hyaloderm layer (contrary to the thin walls in M. emarginata) and the relatively small (12-18 μm wide) mid-leaf cells in M. subemarginata (Bakalin et al., 2019). e observations of the M. subemarginata specimens collected in the Tatras showed that the thickened cell walls of the hyaloderm layer in M. subemarginata seem to be a basic qualitative trait. is observation was based on a perpendicular cross-section of the stem between the leaf bases. When interpreting the image of the stem cross-section, the area where the base of the leaf adheres to the stem should be excluded, because this might be misinterpreted as the hyaloderm (the leaf cells of both species always have thickenings). It seems that M. subemarginata usually has a single-layered hyaloderm, whereas the hyaloderm of M. emarginata has two layers. It is noteworthy that the scleroderm of M. subemarginata is not as well developed as that of M. emarginata. is can be related to the size of both species as well as their habitats. e height of M. subemarginata does not exceed 20 mm (cf. Bakalin et al., 2019), as evidenced by the specimens collected in the Tatras. Marsupella subemarginata grows in humid places, where water periodically slowly drips down rocks. Marsupella emarginata can be found around streams and waterfalls, where water flows more or less rapidly.
According to Bakalin et al. (2019), the color of the plants is another good distinguishing feature. e specimens found in the Tatras were light or dark brown, or rusty, but never red or purple. It seems that the specimens of M. subemarginata from the Tatras have deeper emarginate leaves, which slightly resembled those of M. sphacelata at first glance. However, this trait is not constant, so it is difficult to Acta Societatis Botanicorum Poloniae / 2022 / Volume 91 / Article 917 Publisher: Polish Botanical Society precisely define it in the identification key. To sum up, the specimens of M. subemarginata from the Tatras are small altimontane plants with a height of up to 20 mm. ey are light or dark brown, golden, or rusty in color. e hyaloderm is usually unistratose and composed of thick-walled cells and mid-leaf cells up to 18 μm wide. Unfortunately, the examined herbarium material also contained some specimens which caused identification problems and could not be classified with certainty as the distinguished species.
According to Bakalin et al. (2019), in addition to in Eastern and Northeastern Asia, M. subemarginata might occur in the temperate Atlantic climate zone in Europe. e discovery of this liverwort in the Sudetes and Carpathians extended the range of the species to areas under less influence of the Atlantic climate but with high rainfall. e annual rainfall at the localities of M. subemarginata in the Giant Mts is 1,200-1,400 mm, whereas in the Tatra Mts it is 1,400-2,000 mm (read from the map provided by Ustrnul et al., 2015).
Currently, in total there are 10 plant species of Marsupella in the Tatra Mts, including the newly identified species. Below is the key to their identification.
Key to the Marsupella species occurring in the Tatra Mountains: