Liverworts of Magadan: Life on the Edge of Beringia

Magadan Province, located on the southwestern edge of Greater Beringia, combines various floristic elements in its flora, including Beringian and circum-boreal species. The geographic position and habitat diversity of Magadan Province predicts its liverwort flora is one of the richest hemiarctic floras in Asia. The distribution of species throughout the region is uneven, and while its southern part shows close connections with the suboceanic floras of Kamchatka, the middle and central parts are clearly related to the floras of Chukotka, where the Beringian land bridge directly lies in the past. The wide distribution of basic rocks here leads to the existence of a significant complex of basiphylous taxa. A total of 214 taxa (including 205 species and nine varieties) are reported in the present paper. The study of liverworts of Magadan Province should be continued and several new additions to the floral list are highly likely.


Introduction
Magadan Province is a region in northeast Asia.Most of it is occupied by the Kolyma Plateau, whereas the southern edge is framed by the Sea of Okhotsk.Unlike in the neighboring regions Chukotka, the Republic of Yakutia, Kamchatka Territory and the northern part of Khabarovsk Territory, in this area, with the exception of a narrow strip along the coast, there was almost no indigenous population.This is due to extremely unfavorable living conditions: a small number of wild plants consumed by humans, scarce fish resources, and an ultracontinental climate that dominates most of the region.For a phytogeographer or botanist in a broad sense, Magadan Province is of undoubted interest as a place where tundra-steppe landscapes, similar to those that existed on the Beringian land bridge during the peak of the last glaciation, are preserved over a large area.This is how Magadan Province differs from Chukotka-the central part of the Beringian land bridge in the past.The climate in central Magadan Province has changed little since those times [1,2], while in most of Chukotka, except for the areas adjacent to Magadan Province, it has become much wetter.
The data available in the literature on liverworts of Magadan Province are rather scarce.The first and last checklist of Magadan liverworts was published by Blagodatskikh and Duda [3], including 92 species.This number in itself is not large; moreover, the report describes the distribution of taxa throughout the province quite unsatisfactorily.Historically, even in the 35 years since the publication of the cited checklist, the liverworts of Magadan have remained unstudied except for the efforts of our team.The province does not have "its own" hepaticologist, just as there are none in the neighboring regions, except in Yakutia.Our goal was to conduct a critical assessment of the available literature data, as well as to systematize the material that we collected every year for five years, from 2010 to 2014, in different areas of the region, as well as to analyze the phytogeographical relationships of the studied flora.The results of this effort are presented in the present report.
Plants 2023, 12, 3928 2 of 31 Thus, before this account, fewer than 100 liverwort species were known from Magadan Province, and their knowledge seemed to be significantly less in comparison with what is known from mosses (364 species) [4] and from vascular plants (1441 species) [5].This was one of the arguments to conduct the present research.

General Diversity and Characteristics
A total of 214 taxa were identified, including 205 species and nine varieties.Five species were excluded from the flora.Particularly rare records include Apotreubia nana (interpretation follows Bakalin and Vilnet [6]), a species very rare in hemiarctic Beringia and in northeast Asia, known from Magadan locality only.The calciphilous mesophyte Asterella lindenbergiana, which has a discontinuous circumpolar range, is also rare in northern Asia.The distribution of Barbilophozia rubescens is very poorly studied; in Asian Russia, this is one of the very few localities.
At the northern border of their ranges are Bazzania denudata and B. trilobata.Their locations in Magadan Province are the northernmost in Asia.For Moerckia flotoviana, a suboceanic subcircumpolar boreal-temperate species, this locality is the northernmost in Asia and, apparently, the most continental of those known.The northernmost occurrences of Crossocalyx hellerianus and Scapania apiculata are also found in the studied flora-these boreal circumpolar epixylous taxa rarely penetrate the Asian hemiarctic.The same should be said of Neoorthocaculis attenuatus, although this species was also observed in habitats other than epixylous.A similar situation was observed for Tritomaria exsecta and Tritomaria exsectiformis.The rare boreal, predominantly suboceanic Fuscocephaloziopsis loitlesbergeri is at the northern limit of its range here, and this is one of only a few occurrences of the species in Asia.Frullania austinii (=F.bolanderi s. auct.), a common epiphyte of boreal Pacific Asia, is found here at the northernmost locality in Asia and in an atypical habitat (the identity of the name may be questioned).The distribution of Frullania davurica is also at the northern border here.Very unexpected is a record of Harpanthus scutatus, a mainly temperate suboceanic species, found in typical habitats (decaying wood) but in isolation from its range, which mainly ends in Asia at 50 degrees northern latitude.The hemiboreal Asian, mostly suboceanic Lophozia lantratoviae is also found here at the northern limit of its distribution.The East Asian temperate Mylia verrucosa is known here in isolation from its main range.It should be noted that both these species and the abovementioned taxa of Bazzania are found here only in a narrow strip along the coast, where the climate is much milder than in the interior areas.Conventionally, Metzgeria pubescens belongs to the same group-a species with a wide range but rarely penetrating the hemiarctic.The East Asian temperate Radula obtusiloba was apparently found in relict habitats at the northern border of its distribution, at a significant distance from its area core.Conditionally 'southern' species in the flora, in addition to those mentioned, also include all species of Riccardia, Riccia, and Ricciocarpos.In general, for East Siberian Scapania rufidula, this is also the northernmost location.
At the southern border of its continuous distribution in continental Asia is Cryptocolea imbricata.Although this species even reaches North Sikhote-Alin (48 degrees northern latitude), its locations there are clearly of a relict nature [7].The same should be said of the distribution of Eocalypogeia schusteriana; farther south, the species is found as a relict (for example, in central Sakhalin) [8].Apparently, the Beringian Frullania ignatovii is generally at the southern limit of its distribution in northeast Asia here, although westward, it penetrates farther south to Baikal Siberia [9].Frullania subarctica is very common in the studied area, but its representation in communities is sharply reduced to the south of Magadan Province.Herbertus arcticus, a poorly studied species whose taxonomical status may be questioned, is a typical Beringian species, although it is found farther south in several enclaves of the Beringian flora.The same 'Mega-Beringian' complex includes Lejeunea alaskana, Lophozia schusteriana (presumably a species of taxonomically doubtful status), Marsupella arctica, Neoorthocaulis hyperboreus, Plagiochila arctica, Pseudolepicolea fryei, Radula prolifera, and Scapania ligulifolia.Arctic circumpolar Lophoziopsis rubrigemma and Prasanthus suecicus reflect the Arctic connections of the flora.The southern tip of the Magadan region is the end of the continuous distribution of Mesoptychia sahlbergii, although, in enclaves, this species reaches even the Baikal Lake area.The southernmost localities of Scapania brevicaulis in Asia are also located here.Scapania magadanica deserves special mention-apparently a Beringian species known from areas that could have been nunataks during the Pleistocene-Holocene glaciations [10].In addition, the species also occupies a special position in the Scapania system as a genetically weakly isolated derivate of the strikingly morphologically different Scapania kaurinii.
The suboceanic North Pacific Fuscocephaloziopsis pachycaulis is found here in the most continental climate conditions known for the species.This partly applies to Scapania obscura as well.
The calciphilous complex is quite significant, which is explained by the wide distribution of basic rocks, although they are all of arctic-hemiarctic affinities; there are no southern species among them.Examples include Arnellia fennica, Lophoziopsis pellucida, L. polaris, four species of the genus Mannia, seven species of the genus Mesoptychia (conventionally including M. heterocolpos, although it also grows on substrates other than basic), Odontoschisma macounii, Oleolophozia perssonii, Peltolepis quadrata, Pseudotritomaria heterophylla, Saccobasis spp., Sauteria alpina, and Scapania gymnostomophila.Conventionally, Scapania cuspiduligera, Schljakovianthus quadrilobus, and Sphenolobus cavifolius can be included in this group.

List of Taxa
Taxa in the checklist are arranged alphabetically; the nomenclature follows Söderström et al. [11], with the exception of Solenostomataceae, where a narrow genus concept was adopted, acceptance of Pseudolophozia Konstant.and Vilnet as distinct from Barbilophozia Loeske, the new concept for Schistochilopsis (N.Kitag.)Konstant.according to Bakalin et al. [12], and the narrow species concept for Blepharostoma (Dumort.)Dumort., following [13].Each taxon is annotated with (1) reproductive structures (ant.-antheridia; arch.-archegonia; per.-perianths; spor.-sporophytes; gemm.-gemmae), if present; (2) the altitudinal range, in meters above sea level; (3) collection localities (in accordance with that described in the Section 4.2 of the paper), where abbreviations of the floristic districts are given in bold font; (4) a description of the habitat in the area treated; and (5) a brief citation of literature reports, where present.
Lophozia lantratoviae .Peaty shore of the lake, in the splash zone.Hemiarctic Larix forests.

Doubtful Records (Not Included in Analysis)
Calypogeia azurea Stotler and Crotz-recorded for KOLY by Blagodatskikh and Duda [3].This species does not occur in the Russian Far East in a recent revision by Buczkovska et al. [15], being replaced by the newly described C. orientalis Buczk.et Bakalin.However, the probability of occurrence of C. orientalis in Magadan Province is very low.Moreover, since to the best of our knowledge, all material collected by Blagodatskikh was identified by Duda after drying, the information on oil bodies (the only reliable character for definitively differentiating the taxon from morphologically similar taxa, such as C. muelleriana) was not available to Duda.

Marsupella tubulosa
Steph.-recorded for KOLY by Blagodatskikh and Duda [3] as Marsupella emarginata ssp.tubulosa (Steph.)N. Kitag.However, the identification feature widely used at that time to differentiate it from M. emarginata s. str.(unequal of leaf lobes) in the vast majority of cases is not applicable.The only reliable feature is biconcentric oil bodies (cf.[16]), a feature neglected at that time and not available in previously-dried material.Marsupella tubulosa has a boreal to temperate amphi-Pacific East Asian distribution, with the northernmost confirmed records from East Kamchatka, and the probability of occurrence of this taxon in Magadan Province is very low.
Scapania nemorea (L.) Grolle-recorded for KOLY by Blagodatskikh and Duda [3].However, this taxon does not occur in the Russian Far East [17], and the report most likely belongs to S. crassiretis.
Scapania verrucosa Heeg-recorded for KOLY, O-Kol and OKHO by Blagodatskikh and Duda [3].However, this taxon is not known in the northern part of the Russian Far East (although it is known as a rarity in its southern part).The cited report most likely belongs to S. sphaerifera, a species poorly understood at the time when treatment by Blagodatskikh and Duda [3] was conducted.

Comparison of the Regional Floras in Northeast Asia
The results of the DCA analysis are visualized in Figures 3 and 4. Clustering based on conditional distances (compared to the conditional average, as described in Materials and Methods) is given below.The provided list shows that with the requirement of "three neighbors", clusters are allocated at a threshold value from 20 to 100% (of the length of the matrix average), while two clusters are allocated only at threshold values of 20 and 30%.For larger values, there is only one cluster, which includes more and more floras as the maximum permissible conditional distance increases.With the minimum requirement of "two neighbors", 2 clusters are allocated at 10, 30, 80, and 90%.At 20% of the mean distance, three clusters are identified, and in other cases (40-70%), only one cluster is identified.List of Clusters 10% of mean value distance between compared floras, three neighbors.

Discussion
The present study revealed a fairly high taxonomic diversity of liverworts, surpassing that of Chukotka (177 taxa cf.[18]) and comparable to that of the Republic of Yakutia (215 taxa, including 196 species cf.[19]), despite a much smaller area (562 thousand square kilometers versus three million square kilometers in Yakutia).The diversity of liverworts is somewhat higher in Kamchatka and on adjacent islands (232 species cf.[20]).This difference is quite natural and is explained by a more humid climate and, presumably, by a higher diversity of communities.At the same time, it is obvious that the potential for new records in Magadan Province has not been exhausted.The territory of the province is still studied very unevenly: there are practically no data on the flora of the entire eastern half of the province, where there are types of communities and types of habitats not represented in its western part.
The high taxonomic diversity of liverworts in Magadan Province is explained by its geographical location and natural conditions.The first thing to note is its position within 'Mega-Beringia', as a part of a single area not covered by a continuous glacier and located near the Bering Land Bridge.This circumstance explains the presence of a large number of Beringian and Mega-Beringian taxa.For some of these Beringian taxa, Magadan Province is the largest current enclave of distribution.The second feature that determines the high diversity of the flora is the widespread occurrence of basic rocks (basalts, limestones), which makes the existence of a large basiphylous complex within the flora inevitable.The third important feature is the distribution of almost true boreal forests (with a complex of boreal species, including the epixylous fraction) in the narrow strip along the Sea of Okhotsk, with the dominance, in general, of typical hemiarctic communities at the lower altitudinal levels in most of the area.Moreover, in the upper part of the altitudinal profile, tundra and alpine wastelands are widely developed, which inevitably enrich the flora with arctic-montane species.
When dividing the floras included in the analysis for comparison with both "two neighbors" and "three neighbors", with minimal distance (20-30% of the average conditional distance), two patterns are confirmed: (1) the close connection of the Kolymsko-Okhotsky and Kolymsky floristic districts with the floras of Chukotka and ( 2) the connection of the Okhotsky floristic district of Magadan Province with the hemiarctic suboceanic floras of Kamchatka.When the distance is increased to 40%, almost all boreal, hemiarctic, and even hemiboreal floras included in the analysis (up to the Changbai Mts. and the southern Kurils) are combined into one cluster.Southern warm-temperate (in the lower altitudinal level) floras (mountain systems of South Korea) merge into one cluster with hemiarctic floras only when the minimal distance reaches 100% of the average and this already reflects only the most general relationship of floras in Pacific Asia.
In light of our statements on the incompleteness of the study of the liverwort flora of Magadan Province, it would be appropriate to make a short comparison with the state of knowledge of mosses and vascular plants of this province.The latest checklist of mosses from the Magadan region was published by Pisarenko and Bakalin [4].It includes 364 species of mosses (of which 133 are recorded for the province for the first time).Thus, the number of known species of mosses exceeds the number of known liverworts by less than twice.On the one hand, this may suggest that the state of knowledge of liverworts is higher than that of mosses, and on the other hand, it may suggest that the state of knowledge of mosses is even worse than that of liverworts, because data on liverworts are also incomplete.Data on the distribution of mosses suffer from the same organic incompleteness as data on liverworts: almost all species known in the province are from only the three westernmost districts of the six in the province.And in this sense, their potential diversity has not been fully revealed, as is the case with liverworts.Vascular plants have been studied much better in Magadan Province than mosses and liverworts.The latest summary of flora [5] lists 1441 species of vascular plants (1168 excluding aliens).At the same time, there is significant information on the distribution of vascular plants in the eastern part of the province, although there are still fewer collection points in it than in the western half of the region.The flora of vascular plants of the Magadan region is much richer than the flora of vascular plants of Kamchatka (whereas poorer in mosses and liverworts), which once again emphasizes the untapped potential of bryophyte research in the region.
In the adjacent and huge (six times larger than Magadan Province) Republic of Yakutia, 1965 species of vascular plants are known (that is, 30% more than in Magadan Province) [19].The difference is due to the larger area and probably greater diversity of habitats.However, if one compares the numbers of known species of liverworts and mosses in the Republic of Yakutia, the comparison is not always in favor of the latter.In Yakutia, 196 liverwort species are known (versus 205 in Magadan Province), which can be explained both by incomplete study (a factor characteristic of both regions) and by the fact that taxa with amphi-Pacific area are absent or few in number in the liverwort flora of Yakutia.At the same time, 517 species of mosses are known in Yakutia (versus 364 in Magadan Province), which, in addition to being understudied, can be explained by the lower "importance" of humidity for mosses than for liverworts and the deep penetration of Central Asian species there.
The statistical analysis, as presented in this work, concerns only the Asian part of Beringia and the adjacent areas in Asia.However, apparently, species with a similar range are also common in the Western Hemisphere, in Alaska.Since we have not presented a mathematical comparison of the floras of Magadan Province with Alaska, it seems appropriate to briefly discuss here the connections between the liverwort flora of Magadan and the liverwort flora of Alaska.The liverwort flora of Alaska (excluding the Aleutian Islands) houses 267 species, that is, much richer taxonomically, but also larger in area.In Alaska, as well as in Magadan Province, Apotreubia nana is disjunctively distributed.Asterella lindenbergiana is occasionally found.The poorly studied rare Barbilophozia rubescens is not yet known there, although it may well be found in Alaska.The flora of Alaska has a larger number of species of more southern distribution.For example, the genus Bazzania is represented there by five species, versus two in Magadan Province.Moreover, it should be noted that species known from Alaska, but not known in Magadan Province, can hardly be expected on the territory of the latter.Crossocalyx hellerianus and Scapania apiculata, known in Pacific Asia from the northernmost points in Magadan Province, are known in Pacific America from Alaska.The same must be said about the penetration of Neoorthocaulis attenuatus, Tritomaria exsecta, T. exsectiformis, etc. to the north.Rare, as in Magadan Province, is Fuscocephaloziopsis loitlesbergeri.Harpanthus scutatus, known from Magadan Province (although highly distanced from the area core and generally extremely unexpected here), is not known in Alaska.Lophozia lantratoviae is also unknown in Alaska.It is unlikely to be found there.This is a hemiboreal Asian species that does not penetrate America.While recently described Lophozia fuscovirens, a little-known taxon, can be found in Alaska as well, Mylia verrucosa, an East Asian temperate species, is also unknown in Alaska and unlikely to be expected.The montane Asian Scapania rufidula is also absent from Alaska.The East Asian Radula obtusiloba is replaced in Alaska by the vicarious Radula polyclada (differences between the two taxa have not been reliably tested).Beringian and conditionally Beringian (possessing, in general, a wider range, but whose core is located in Beringia) closely connect Alaska and Magadan Province.This group is represented by Cryptocolea imbricata, Eocalypogeia schusteriana, Frullania subarctica, Herbertus arcticus, Lejeunea alaskana, Lophozia schusteriana, Marsupella arctica, Plagiochila arctica, Pseudolepicolea fryei, Radula prolifera, Scapania ligulifolia.Probably, Frullania ignatovii should also be included there, if we assume that the information about F. eboracensis Lehm.from Alaska actually belong to F. ignatovii.Scapania magadanica, so far known only from the Magadan region and Kamchatka, is probably a Beringian species; however, it is quite possible that it is limited to the Asian part of Beringia.The flora of Alaska turns out to be richer, largely due to more moisture-dependent and presumable temperate taxa.It is unlikely that the following species known in Alaska will ever be found in Magadan Province: Acrobolbus ciliatus (Mitt.)Schiffn., Anastrepta orcadensis (Hook.)Schiffn., Cololejeunea macounii (Spruce) A. Evans, Douinia imbricata (M.Howe) Constant.et Vilnet, Metzgeria leptoneura Spruce, Nardia compressa (Hook.)Gray, Plagiochila semidecurrens (Lehm.et Lindenb.)Lindenb., Pleurozia purpurea Lindb., etc.At the same time, finding several species that are not yet known in Magadan Province, but are found in Alaska, is quite possible in Magadan Province.This applies to Anastrophyllum assimile (Mitt.)Steph., Ascidiota blepharophylla C. Massal., Gymnocolea fascinifera Potemkin, Gymnomitrion mucrophorum R.M. Schust., Hygrobiella laxifolia (Hook.)Spruce, etc.The latter comparison shows that still there are several taxa that can be found in Magadan Province, but, in any way, their number is much less than is known to be found in Alaska.

Study Area
Since the description of the study area was given in detail earlier in a paper devoted to Magadan mosses [4], only the most important features need to be mentioned here.
Historically, Magadan Province was never covered by shield glaciation.Glaciation, if present, had a network or mountain-valley character.In addition, it should also be taken into account that the southern tip of Magadan Province, now washed by the waters of the Sea of Okhotsk, was a purely continental region during the maritime regressions.The coastline was located 100 km or more to the south, neither Gizhiga Bay nor Penzhina Bay in the modern sense existed, and this vast space was united by land with the territory of the modern isthmus of the Kamchatka Peninsula.Thus, the climate was ultracontinental throughout the current borders of Magadan Province, supporting the existence of tundrasteppes, which have remained under slightly altered conditions to the present day [1,2].
A peculiar feature of Magadan Province is the wide distribution of neutral (shales are the most common) and alkaline (limestones, basalts) substrates, including various combinations of both types.Acidic rocks, such as granites, are distributed locally, which invariably leads to the relative rarity of some acidophilous taxa commonly widespread in the hemiarctic.Over most of the region, mid-mountain relief is developed.At the same time, the mountains have a smoothed appearance ('Goletz' type), with a flat top and gentle slopes.More or less extensive bedrock outcrops are found only sporadically.The highest localities of the province are the Snezhnaya (2293 m) and Aborigen (2286 m) mountains, although in general, there are numerous peaks either almost reaching or slightly exceeding 2000 m above sea level.
A striking feature of Magadan Province is its continental climate with minimal precipitation.In the south of Magadan Province, the amount of precipitation reaches 660 mm per year (half in the form of liquid precipitation, https://en.climate-data.org/asia/russianfederation/magadan-oblast/magadan-986641/accessed on 15 August 2023), while in the interior lands of the province, the amount of precipitation drops to 417 mm per year (Seymchan, https://en.climate-data.org/asia/russian-federation/magadan-oblast/seymchan-52370/accessed on 15 August 2023) and even 306 mm per year (Jack London Lake [21]).However, a particular lack of moisture is usually not observed due to the commonness of horizontal precipitation and low summer temperatures.The average annual temperature varies from −2 • C on the coast to −11 • C inland.Summer is short, and the frost-free period is either absent or reaches 100 days in coastal areas.Near the western border of Magadan Province is the cold pole of the Northern Hemisphere (Oymyakon Settlement); in the interior areas of the province, minimum temperatures often drop below −60 • C in January.The average temperature of the warmest month varies from +12 to +15 • C on the plains and in the valleys, falling with elevation and reaching only +7.9 • C on the slopes of Aborigen (Susuman district) at an altitude of 1650 m above sea level [20].Meanwhile, on clear sunny days in mid-July, daytime temperatures in the interior areas of the province can rise to +30 • C and even higher.The entire region, except for the narrow coastal strip, is located in an area of continuous permafrost.
The zonal vegetation in the territory of Magadan Province is hemiarctic, mainly represented by sparse Larix cajanderi Mayr forests and thickets of Pinus pumila (Pall.)Regel.Moreover, Pinus pumila commonly does not form impassable thickets, but due to the low height of snow cover, it forms open communities growing in small clumps, usually less than 1-1.5 m in height.In the narrow coastal strip, however, well-developed forest communities are formed, sometimes with a dense undergrowth of Pinus pumila, and have a transitional character to the boreal type.In addition, it is necessary to mention small (mainly only in the riparian zone) communities of Betula lanata (Regel) V.N.Vassil.and floodplain forests in wide valleys, sometimes including Populus L. and Chosenia Nakai, but often limited to various species of Salix L. Above the crooked forests, either gravelly wastelands or various types of tundra are developed, of which the most common types are lichen and hummocky dwarf shrub-moss tundras.Peat accumulation in waterlogged communities in the region either does not occur or occurs slowly, so the distinctions between wet tundra and swamps are blurred.Floristic regionalization of Magadan Province was developed by Khokhrjakov [22] and confirmed by Berkutenko et al. [5].The boundaries of the regions have a sublatitudinal extension and reflect a trend of increasing continentality rather than decreasing temperature.

Data
The data used to compile this checklist were literature data and our own collected specimens, as well as small collections loaned to us by our colleagues.
As mentioned above, the first and only list of liverworts published to date for Magadan Province is that by Blagodatskikh and Duda [3], and it includes 92 species.At the same time, Scapania obcordata is given by the authors only for the coast of Chaun Bay, on the coast of the East Siberian Sea, and not belonging to Magadan Province.Thus, the list contains information on the distribution of 91 species within the current borders of the province.The cited list is based on extremely limited literature data, as well as materials collected by Blagodatskikh and identified by Duda during the 15 years of previous work by Blagodatskikh in Magadan Province.It should be noted that Blagodatskikh was a bryologist in the narrow sense; that is, she worked mainly with mosses and collected liverworts along the way, which of course, affected the knowledge of the flora.Some of the specimens from the Blagodatskikh collection are in the herbarium of the LE (St.Petersburg), some are in the herbarium MAG (Magadan), duplicates of the collection are in the Duda Herbarium (Prague), and some are probably lost, so we did not check the questionable species reports.Most of the districts of Magadan Province are very poorly accessible, and therefore, the available data cover only half of the province.
After the publication of the first checklist by Blagodatskikh and Duda [3], certain species were mentioned in taxonomic works on Russian Far East liverworts [17,[23][24][25], etc.Our collections were carried out every year from 2010 to 2014, covering three floristic districts (out of 6).Data on the collection localities are presented in Table 1 and shown on the map (Figure 5).A total of approximately 3000 specimens were collected, approximately 20% of which were studied in the living state and thus for which information on oil bodies was available.For each collected specimen, geographic coordinates, elevation above sea level, vegetation type, substrate, moisture, and light conditions were recorded.Bakalin, 2010Bakalin, , 2012Bakalin, -2014;;Bakalin and Choi, 2011  The areas of OMOL, G-Omol, GIZH floristic districts were not studied.Floristic regionalization followed to Khokhrjakov [22] and Berkutenko et al. [5].

Phytogeographic Relationship Analysis
Floral relationship analysis was carried out using detrended correspondence analysis (DCA), which is applicable for datasets of various sizes and has been tested by us several times for amphi-Pacific liverwort floras [26][27][28][29][30].The material for the analysis was our compiled matrix (Supplementary Table S1) of the species composition of floras, which is a summary species distribution of the compared floras, where the presence of a species is marked with the number 1, and its absence with the number 0. First, the coordinates in a three-dimensional grid were calculated for each of the compared floras (Supplementary Table S2), and then the distances between the floras were determined (Supplementary Table S3).The results were visualized in chart format, where the third axis is shown as a color gradient from red to blue.Given the features of the program, the abscissa is of primary importance for comparison, followed by the ordinate and, finally, the third axis, expressed in the diagram by a color gradient.Based on the distances between floras, the average value was calculated, and the relative distance between each of the floras included in the analysis was determined as a percentage of the average.Based on the relative lengths of the distances, clusters were identified, including floras, each of which is associated with at least x other floras at y% of the largest distance.X varied from 1 to 2, and y-from 10% to 100%.Therefore, the minimal number of clustered floras where x = 1 is two, while that where x = 2 is three.
The compared floras were selected based on two principles: territorial proximity to Magadan Province and revealed level (at least 75 species).In the matrix, we were forced to combine the floras compiled for floristic districts and well-studied 'local' floras.At the same time, regional liverwort floras of Magadan Province were included.This was done for the following reasons: (1) accessible and relatively complete information on the liverworts of Chukotka (i.e., the region with which comparison was especially important in the present work) is available for floristic districts only; (2) the studied localities in Magadan Province often do not fit the definition of 'well-studied' and to obtain more or less reliable information must be combined with nearby ones; (3) several floras included were not within Chukotka and Magadan Province, although they are 'local', in fact reflecting the flora of the entire region (for example, Southern Kamchatka, Central Kamchatka, etc.); and (4) floristic regionalization for the transition zone between the circumboreal region and the East Asian region is not carefully developed, especially in light of the fact thause the patterns of liverwort distribution differ from the patterns of distribution of vascular plants (cf.[31]).All floras involved in the analysis are described in Table 2.

Plants 2023 , 33 Figure 3 .
Figure 3.Comparison of the regional flora distribution in the DCA bubble chart (the third axis is the color gradient from deep blue to deep red).

Figure 3 .
Figure 3.Comparison of the regional flora distribution in the DCA bubble chart (the third axis is the color gradient from deep blue to deep red).

Figure 3 .
Figure 3.Comparison of the regional flora distribution in the DCA bubble chart (the third axis is the color gradient from deep blue to deep red).

Figure 4 .
Figure 4. Distances between floras in Pacific Asia.The degree of proximity of floras, in comparison with the average distance, is highlighted by a color scheme from bright pink for the closest (starting from 8% of the total distance), through intermediate (white) to the most distant (blue, with a maximum of 288% of the total distance).

Table 2 .
Floras involved in the analysis.