Cyanobacterial Diversity of the Northern Polar Ural Mountains

: This study provides new results from an inventory of cyanobacterial species from the Northern Polar Ural Mountains. The article also compiles all existing published data on the cyanobacterial diversity of the region. This ecoregion is located in a unique geographical position in the transition between the sub-Arctic and low Arctic zones and heterogeneous natural conditions. Likely, the unexplored biodiversity of this area’s terrestrial cyanobacteria is high. In total, 52 localities were studied, with 232 samples collected. Cyanobacterial samples were studied under a light microscope. Species were identiﬁed based on morphological characteristics only. A total of 93 species of cyanobacteria were identiﬁed in different habitats; 70 species were found on wet rocks, 35 on the shores of water bodies, 27 in slow streams, and 21 on waterfalls. In total, 37 species are reported as part of the Ural ﬂora for the ﬁrst time, while three species ( Chroococcus ercegovicii , Gloeocapsopsis cyanea , Gloeothece tepidariorum ) were detected in Russian territory for the ﬁrst time. The composition of the cyanobacterial ﬂora of the Polar Urals was compared with the ﬂora of the nearby Arctic and sub-Arctic regions. According to the Sorensen similarity index, the Polar Urals’ ﬂora is more like the ﬂora of Nenets Autonomous Okrug.


Introduction
Cyanobacteria make up an important component of extreme Arctic environments. They are of fundamental ecological importance since they contribute to both carbon and nitrogen fixation and are often the dominant primary producers in polar ecosystems. Local cyanobacterial flora are sources of information for nature conservation and environmental monitoring. The diversity and distribution of cyanobacteria are still poorly understood in Northern Russia [1].
The study of cyanobacterial diversity is important to consider different microbial distribution patterns [2]. Morphological and anatomy traits are the main criteria for classifying and identifying cyanobacteria. Recent studies have shown that traditional cyanobacterial "morphospecies" are comprised of different taxonomic species [3][4][5][6][7]. On the other hand, many cyanobacterial taxa do not have gene sequence data. Widespread taxa, such as Dichothrix, Petalonema, and Stigonema, are cultivation-resistant genera. Only a small number of genotypes of typical terrestrial cyanobacteria, such as Chroococcus, Gloeocapsa, and Gloeocapsopsis, were evaluated. Most of the data about biodiversity accumulated in previous studies are based on the morphological method of identification. Obviously, reliable morphological species identification of the Arctic's cyanobacteria is challenging. An integrative approach including 16S rRNA gene and ITS sequence data, detailed observations of various life stages, correct comparative ecological studies, and geographic distribution could obtain the most accurate estimation of diversity. That method, as a tool for next generation sequencing (NGS), will be able to uncover cyanobacterial diversity of natural assemblages. Currently, NGS results provide a high number of abstract organizational taxonomic units [4]. Unidentified units cannot be used for ecological or geographical tional taxonomic units [4]. Unidentified units cannot be used for ecological or geogra ical studies. Perhaps in transition, the use of "morphospecies" as surrogate units wo be helpful in biodiversity surveys.
The Urals are situated on the border of Europe and Asia and are characterized unique natural conditions. The Polar Urals, located north of the Arctic Circle, are northernmost part of the giant Urals Ridge.
The total known cyanobacterial diversity of the Polar Urals was 156 species bef our work. In previous studies, mostly aquatic ecotopes and soil biocrusts were inve gated. At the same time, cyanobacteria of terrestrial habitats in the Polar Urals rem insufficiently researched. The species distribution in the territory of the mountain ma has not been revealed. The floristic relationship between the cyanobacterial flora of Polar Urals and the flora in other Arctic and sub-Arctic regions has not been analyzed The purpose of this study was to conduct a field exploration of the northern Urals of Polar region and to determine the biodiversity of cyanobacteria.

Characteristics of the Study Area
The investigated area is situated on the northern part of the Polar Urals ( Figure   The western slope is steeper and dissected by rivers and streams much more than eastern one [19]. Along with plateau-like peaks, ridges with typical alpine relief forms widely developed here. The highest of them in the northern part is the Ochenyrd rid There are a few cirque glaciers on the northern exposure slopes [20].
The northern part of the Polar Urals is situated within a field of limestones with sh and trachybasalts [21].
The climate of the area is cold and continental with permafrost and a mean summ temperature range between 10 and 13 °C in the adjacent lowlands. The average ann The western slope is steeper and dissected by rivers and streams much more than the eastern one [19]. Along with plateau-like peaks, ridges with typical alpine relief forms are widely developed here. The highest of them in the northern part is the Ochenyrd ridge.
There are a few cirque glaciers on the northern exposure slopes [20].
The northern part of the Polar Urals is situated within a field of limestones with shale and trachybasalts [21].
The climate of the area is cold and continental with permafrost and a mean summer temperature range between 10 and 13 • C in the adjacent lowlands. The average annual temperature in different areas ranges from −6 to −9 • C. The period with temperatures above 0 • C lasts about 60 days from June 21 to August 21 [22]. Precipitation is uneven on the macroslope. The annual precipitation on the western macroslope is up to 1500 mm. On the eastern macroslope, it is 600-800 mm.
The northern part of the Polar Urals is entirely located in the zonal tundra. The mountains have explicit altitudinal vegetation belts. That altitudinal zonation is composed of two belts: the lower parts of the mountain slopes up to 500-600 m a.s.l. are occupied by the mountain tundra belt, the higher area is the stony barren (golets) belt [23].

Materials and Methods
In 2019, expeditions studied a total of 52 localities ( Figure 2, Table 1) and 232 samples were collected. Altogether, 10 types of habitats were distinguished: (i) bottoms of lakes, (ii) pools in tundra, (iii) fast running streams, (iv) waterfalls, (v) slow running streams in tundra, (vi) shores of a water bodies, (vii) outliers, (viii) wet soils, (ix) wet and dripping rocks, and (x) bare patches of permafrost stock. temperature in different areas ranges from −6 to −9 °C. The period with temperatures above 0 °C lasts about 60 days from June 21 to August 21 [22]. Precipitation is uneven on the macroslope. The annual precipitation on the western macroslope is up to 1500 mm. On the eastern macroslope, it is 600-800 mm. The northern part of the Polar Urals is entirely located in the zonal tundra. The mountains have explicit altitudinal vegetation belts. That altitudinal zonation is composed of two belts: the lower parts of the mountain slopes up to 500-600 m a.s.l. are occupied by the mountain tundra belt, the higher area is the stony barren (golets) belt [23].

Materials and Methods
In 2019, expeditions studied a total of 52 localities ( Figure 2, Table 1) and 232 samples were collected. Altogether, 10 types of habitats were distinguished: (i) bottoms of lakes, (ii) pools in tundra, (iii) fast running streams, (iv) waterfalls, (v) slow running streams in tundra, (vi) shores of a water bodies, (vii) outliers, (viii) wet soils, (ix) wet and dripping rocks, and (x) bare patches of permafrost stock.  Table 1. The species identification was based only on morphological features. The collected natural samples were observed under an AxioScope A1© (Carl Zeiss Microscopy GmbH, Germany) light microscope with the Nomarski interference contrast and ProgRes Speed XT Core 3© camera (Jenoptik©, Germany). AxioVision© software (Carl Zeiss Microscopy GmbH, Germany) was used for measuring morphology. The species identification was performed following modern manuals [24][25][26]. New taxonomic revisions have been taken into account also [6]. The storage of samples is provided by the herbarium at the Polar-Alpine Botanical Garden-Institute (KPABG). Information on habitats, description of localities, and photographs are included in the CRIS database (http://kpabg.ru/cyanopro/, accessed on 1 October 2021) [27,28]. That information system and the GBIF (http://gbif.org, accessed on 1 October 2021) portal were used for the analysis of species distribution in the Arctic and the sub-Arctic. QGIS (GNU General Public License) software was used for maps creation.
The frequency of species occurrence (constancy) was calculated by the formula [29]: B = (a/A) × 100%, where B is the species occurrence, a is the number of samples containing this taxon, and A is the total number of samples.
The similarity of local flora was determined with the Sørensen index (KS) (weighted pair group method using arithmetic averaging) in the program module, ExelToR [30], which used as a plugin for Microsoft Excel©.
where a-number of species common to both sets, b-number of species unique to the first set, c-number of species unique to the set.

Results and Discussion
A summary of cyanobacterial species found in the northern Polar Ural Mountains is given in Table 2. A total of 93 cyanobacterial taxa were identified across the various habitats of the investigated area. In total 37 species are reported in the Polar Ural flora for the first time.  Additionally, three species were detected in Russian territory for the first time. Chroococcus ercegovicii (Figure 3a) were found in aerophytic habitats of limestone outcrops in Croatia and the Czech Republic ( Figure 4). Their population in the Polar Urals grows on a wet wall of rock at a slope of the northern exposure. Perhaps the spatial distribution of this species is linked with the location of calcium rocks. Additionally, three species were detected in Russian territory for the first time. Chroococcus ercegovicii (Figure 3a) were found in aerophytic habitats of limestone outcrops in Croatia and the Czech Republic ( Figure 4). Their population in the Polar Urals grows on a wet wall of rock at a slope of the northern exposure. Perhaps the spatial distribution of this species is linked with the location of calcium rocks. Gloeocapsopsis cyanea (Figure 4) is another species which was newly discovered in the area. It was identified based on the description of the species from the rock wall of a cave entrance on the island of Crete and was also found in Ukraine, the USA, and the Svalbard archipelago. In the Polar Urals, it was found on a wet wall of rock on a slope of the north exposure.  The third of the new recorded species in Russia is Gloeothece tepidariorum. This taxon is widely distributed. Occurrences of this taxon are recorded in Germany, Scandinavia, the Czech Republic, Greece, the USA, Argentina, Uruguay, and China. The species was found in a typical aerophytic habitat on a wet rock.
An uncommon species is Chlorogloea purpurea. It was identified from a sample from the bottom of a lake in the Austrian Alps [31]. This species was also found in the southern Urals in the Republic of Bashkortostan [32] in a terrestrial habitat (Figure 4). In the Polar Urals, Chlorogloea purpurea grows on a biocrust assemblage on fine earth.
As a result of the flora inventory, 37 taxa of cyanobacteria are reported here for the first time in the Polar Urals. Additionally, a few of them are new records for the Arctic. The distribution of these species in the Arctic and the sub-Arctic is given below.
Aphanocapsa fonticola is a montane species, widespread in Europe's mountains; in the Arctic and sub-Arctic, it is found in Svalbard, Norway, and the Murmansk region. The taxon can also be found in China.
A. parietina is a multizonal species which is widespread in Europe. In the Arctic, the species is found on Svalbard, in the Bolshezemelskaya tundra, on the Taimyr peninsula, and in the Kolyma basin. To the south, it is found in the Murmansk region of the Subpolar Urals.
A. rivularis is an arctic-boreal-montane species; in the Arctic, it is found on Svalbard, in the tundra zone of the Murmansk region, the Bolshezemelskaya tundra, Yakutia, and Alaska.
Aphanothece pallida has a cosmopolitan distribution. In the Arctic, the species was found on the Novaya Zemlya Archipelago and in Alaska. In the sub-Arctic, it occurs in the Murmansk region and Norway. It is also sporadically distributed in the Czech Republic, Germany, France, and the Azores islands.
Calothrix breviarticulata is a species with an unclear distribution, in the Arctic it is sporadically found in Svalbard, while in the sub-Arctic, it is found only in the Murmansk region.
Chlorogloea purpurea is a montane species whose distribution is given above. Chroococcopsis epiphytica is also a montane species. This occurrence is the first record of the taxon for the Arctic area. In the sub-Arctic, the species is known to occur in the Gloeocapsopsis cyanea (Figure 4) is another species which was newly discovered in the area. It was identified based on the description of the species from the rock wall of a cave entrance on the island of Crete and was also found in Ukraine, the USA, and the Svalbard archipelago. In the Polar Urals, it was found on a wet wall of rock on a slope of the north exposure.
The third of the new recorded species in Russia is Gloeothece tepidariorum. This taxon is widely distributed. Occurrences of this taxon are recorded in Germany, Scandinavia, the Czech Republic, Greece, the USA, Argentina, Uruguay, and China. The species was found in a typical aerophytic habitat on a wet rock.
An uncommon species is Chlorogloea purpurea. It was identified from a sample from the bottom of a lake in the Austrian Alps [31]. This species was also found in the southern Urals in the Republic of Bashkortostan [32] in a terrestrial habitat (Figure 4). In the Polar Urals, Chlorogloea purpurea grows on a biocrust assemblage on fine earth.
As a result of the flora inventory, 37 taxa of cyanobacteria are reported here for the first time in the Polar Urals. Additionally, a few of them are new records for the Arctic. The distribution of these species in the Arctic and the sub-Arctic is given below.
Aphanocapsa fonticola is a montane species, widespread in Europe's mountains; in the Arctic and sub-Arctic, it is found in Svalbard, Norway, and the Murmansk region. The taxon can also be found in China.
A. parietina is a multizonal species which is widespread in Europe. In the Arctic, the species is found on Svalbard, in the Bolshezemelskaya tundra, on the Taimyr peninsula, and in the Kolyma basin. To the south, it is found in the Murmansk region of the Subpolar Urals.
A. rivularis is an arctic-boreal-montane species; in the Arctic, it is found on Svalbard, in the tundra zone of the Murmansk region, the Bolshezemelskaya tundra, Yakutia, and Alaska.
Aphanothece pallida has a cosmopolitan distribution. In the Arctic, the species was found on the Novaya Zemlya Archipelago and in Alaska. In the sub-Arctic, it occurs in the Murmansk region and Norway. It is also sporadically distributed in the Czech Republic, Germany, France, and the Azores islands.
Calothrix breviarticulata is a species with an unclear distribution, in the Arctic it is sporadically found in Svalbard, while in the sub-Arctic, it is found only in the Murmansk region.
Chlorogloea purpurea is a montane species whose distribution is given above.
Nostoc caeruleum is considered cosmopolitan. In the Arctic, it grows in the Malozemelskaya tundra, the Novaya Zemlya, Yakutia, and the New Siberian Islands. In the sub-Arctic, it occurs in the Murmansk region, Karelia, and the Subpolar Urals.
Phormidiochaete nordstedtii has an arcto-boreal distribution. In the Arctic, this species occurs in Greenland and Svalbard. In the sub-Arctic, it is found in Norway, Sweden, and the Murmansk region.
Phormidium kuetzingianum is a cosmopolitan species. In the Arctic, the species has been recorded in Svalbard, the Malozemelskaya tundra, and Chukotka, while it is found in the Murmansk region and the Subpolar Urals in the sub-Arctic.
Pseudanabaena minima is a species with an unclear distribution, which is found in the Arctic in Svalbard and the sub-Arctic Murmansk region.
Rivularia haematites (Figure 3b) is an arcto-boreal species; in the Arctic it is found in the Canadian Arctic Archipelago, Alaska, Novaya Zemlya, and the Bolshezemelskaya tundra. This taxon is also recorded in the sub-Arctic in the Murmansk region.
Schizothrix lardacea has a cosmopolitan distribution. In the Arctic, the species has been recorded in Svalbard, the Bolshezemelskaya tundra, and the Yamal peninsula. In the sub-Arctic, it is found in the Murmansk region, Krasnoyarsk Kray, Kamchatka, and the Commander Islands.
Siphononema polonicum is a montane species. In the Artic, the species grows in Svalbard and Yakutia; in the sub-Arctic, it occurs in Norway and the Subpolar Urals. In Europe, it is common in the Alps and the Tatras.
Scytonema mirabile is a cosmopolitan species. In the Arctic, it is known to be on Ellesmere Island and the Bolshezemelskaya tundra. In the sub-Arctic, it is found in Norway, Sweden, the Murmansk region, and the Subpolar Urals.
Symplocastrum friesii is also cosmopolitan. The species is widely distributed in the Arctic: Svalbard, Franz Josef Land, the Eastern European tundra, in the vicinity of Labytnangy town, on Yamal, Taimyr, and Severnaya Zemlya. In the sub-Arctic, it is found in the Murmansk region, Karelia, the Subpolar Urals, Krasnodar Kray, Magadan Region, Kamchatka, and the Commander Islands.
Trichocoleus delicatulus is a species with an unclear distribution. The species is found in the flora of Svalbard, though it has not been recorded in the Arctic or in other sub-Arctic locations. The species was also identified in England and in Greece.
T. sociatus has a cosmopolitan distribution. In addition to the Polar Urals, the species is found in the Arctic in the Svalbard Archipelago and on Queen Elizabeth Island (Canadian Arctic Archipelago). It is known to be in the following locations in the sub-Arctic: the Murmansk region, Krasnodar Kray, and the Magadan Region.
The common, widespread species in most of the studied habitats are Phormidesmis sp. (the frequency of species occurrence-24.3%), Gloeocapsa violascea (23%) (Figure 5a), Stigonema minutum (19.1%), Calothrix parietina (18.7%), Gloeocapsopsis magma (16.1%), Nostoc commune (13.9%), Gloeocapsa sanguinea (13%), Tolypothrix tenuis (13%), Petalonema incrustans (12.2%) (Figure 5b), and Gloeocapsa kuetzingiana (10.9%) ( Table 2). Mostly, these are species that both occupy rocky habitats and can grow on fine earth. The greatest number of species (70) was found on wet rocks and on the shores of lakes and streams (35) (Figure 6). This species distribution by habitat is also typical for the flora of other regions of the Arctic. In the flora of local areas of Svalbard, rocks are most often characterized by high species diversity [36,37]. The characteristic feature of the Polar Urals' flora is a lack of cyanobacterial species in typical habitats such as seepages. Usually, the species richness in seepages is secondary to other habitats. Seepages are characterized by stagnant or slowly flowing water from snowmelt. They occur in over-moistened locations on gentle slopes or terraces. This type of habitat, although rare, is found in the Urals. However, this niche is occupied by bryophytes that outcompete cyanobacteria. Most of the identified taxa (59 species) are occasionally distributed in the studied area and occur with a frequency of 0.4% to 1.7% (Figure 7). This is similar to the species distributions of other explored Arctic regions. This peculiarity was noted for local areas of Sval- The greatest number of species (70) was found on wet rocks and on the shores of lakes and streams (35) (Figure 6). This species distribution by habitat is also typical for the flora of other regions of the Arctic. In the flora of local areas of Svalbard, rocks are most often characterized by high species diversity [36,37]. The characteristic feature of the Polar Urals' flora is a lack of cyanobacterial species in typical habitats such as seepages. Usually, the species richness in seepages is secondary to other habitats. Seepages are characterized by stagnant or slowly flowing water from snowmelt. They occur in over-moistened locations on gentle slopes or terraces. This type of habitat, although rare, is found in the Urals. However, this niche is occupied by bryophytes that outcompete cyanobacteria. The greatest number of species (70) was found on wet rocks and on the shores of lakes and streams (35) (Figure 6). This species distribution by habitat is also typical for the flora of other regions of the Arctic. In the flora of local areas of Svalbard, rocks are most often characterized by high species diversity [36,37]. The characteristic feature of the Polar Urals' flora is a lack of cyanobacterial species in typical habitats such as seepages. Usually, the species richness in seepages is secondary to other habitats. Seepages are characterized by stagnant or slowly flowing water from snowmelt. They occur in over-moistened locations on gentle slopes or terraces. This type of habitat, although rare, is found in the Urals. However, this niche is occupied by bryophytes that outcompete cyanobacteria. Most of the identified taxa (59 species) are occasionally distributed in the studied area and occur with a frequency of 0.4% to 1.7% (Figure 7). This is similar to the species distributions of other explored Arctic regions. This peculiarity was noted for local areas of Sval- Most of the identified taxa (59 species) are occasionally distributed in the studied area and occur with a frequency of 0.4% to 1.7% (Figure 7). This is similar to the species distributions of other explored Arctic regions. This peculiarity was noted for local areas of Svalbard [36][37][38][39][40] and the Murmansk region [34]. The reason for the spatial distribution of cyanobacterial species in the local area is microenvironmental conditions that favor their growth. Mosaic environmental conditions have the greatest impact on cyanobacterial species composition. bard [36][37][38][39][40] and the Murmansk region [34]. The reason for the spatial distribution of cyanobacterial species in the local area is microenvironmental conditions that favor their growth. Mosaic environmental conditions have the greatest impact on cyanobacterial species composition. The distribution of species diversity in terms of elevation is a normal distribution ( Figure 8). This study has shown that most of the species are found at elevations 400-600 m above sea level within the mountain tundra belt. The cyanobacterial species diversity decreases during the transition from the mountain tundra belt to the golets belt, reflecting an increase in extreme environmental conditions. The correlation coefficient between the number of species in a given habitat and its height is −0.53, indicating a significant influence of habitat height on species richness. A notable reduction in the diversity of soil algae in Arctic flora was found approaching mountain peaks [14]. The distribution of species diversity in terms of elevation is a normal distribution ( Figure 8). This study has shown that most of the species are found at elevations 400-600 m above sea level within the mountain tundra belt. The cyanobacterial species diversity decreases during the transition from the mountain tundra belt to the golets belt, reflecting an increase in extreme environmental conditions. The correlation coefficient between the number of species in a given habitat and its height is −0.53, indicating a significant influence of habitat height on species richness. A notable reduction in the diversity of soil algae in Arctic flora was found approaching mountain peaks [14]. bard [36][37][38][39][40] and the Murmansk region [34]. The reason for the spatial distribution of cyanobacterial species in the local area is microenvironmental conditions that favor their growth. Mosaic environmental conditions have the greatest impact on cyanobacterial species composition. The distribution of species diversity in terms of elevation is a normal distribution ( Figure 8). This study has shown that most of the species are found at elevations 400-600 m above sea level within the mountain tundra belt. The cyanobacterial species diversity decreases during the transition from the mountain tundra belt to the golets belt, reflecting an increase in extreme environmental conditions. The correlation coefficient between the number of species in a given habitat and its height is −0.53, indicating a significant influence of habitat height on species richness. A notable reduction in the diversity of soil algae in Arctic flora was found approaching mountain peaks [14]. Habitats located in valleys and at the foot of mountains are characterized by a specific floral composition. Species typical for benthic communities at the bottom of rivers (Chamaesiphon minutus, Rivularia haematites) and riverside and coastal rocks have been observed here (Calothrix breviarticulata, Nostoc caeruleum, Phormidium kuetzingianum, Symplocastrum friesii). These are not found in the upper belts.
A middle part of the mountain's slopes (200-600 m) in the Polar Urals is characterized by the highest cyanobacterial diversity due to both the diversity of habitats and lower pressure of competition from other plants.
Lower species abundance is observed in the upper golets belt. Under mountainous conditions up to 1000 m.a.s.l., species of Leptolyngbya cf. gracillima, Phormidiochaete nordstedtii, Stigonema minutum, Microcoleus autumnalis, and Chroococcus cohaerens are the only cyanobacterial inhabitants. The harsh environment of the golets belt supports fewer species than the mountain tundra belt.
The habitats in the upper belt are characterized by extreme environmental gradients, oscillating temperatures and humidity, and soil dryness. These factors complicate the development of cyanobacteria. The harsh environments are the primary reason for decreased diversity of cyanobacterial assemblages. In addition to the negative impact on the species composition of cyanobacteria, an extreme impact is also shown on the sparse vegetative cover, the decreased role of flowering plants, and significant proportions of projective coverings of lichens and lithophilic mosses [41][42][43].
We combined our research data with previously published data on the flora of the Polar Urals. Currently, the known cyanobacterial diversity of the Polar Urals is 179 species. Despite the small area of the Polar Urals, this territory is rich in cyanobacterial flora. The flora of this region exceeds that of most of the studied regions of the Eurasian part of the Arctic. It is second only to the flora of Svalbard [44] and the Nenets Autonomous The species richness could be explained by diverse mountain conditions (considerable altitudinal range and diverse landscapes), as well as the relatively low latitude of the Polar Ural region. In addition, an important reason for the high diversity is that the northern part of the Ural region has been well studied compared to other Arctic areas.
According to the Sorensen similarity index, based on the cyanobacterial floral composition, the Polar Urals' flora is more similar to the floras of the nearby regions, Nenets AO (similarity is 54%) and Svalbard (51%) (Table 3, Figure 9).  A cluster analysis of the flora of the Arctic territories shows that the flora of the nearby regions of the Polar Urals, Subpolar Urals, and Nenets AO, which are close in climatic and geological conditions, are combined into one clade ( Figure 10). A cluster analysis of the flora of the Arctic territories shows that the flora of the nearby regions of the Polar Urals, Subpolar Urals, and Nenets AO, which are close in climatic and geological conditions, are combined into one clade ( Figure 10).
The studied flora also has a high similarity to the flora of Svalbard (51%), the sub-Arctic part of the Murmansk region, and the Subpolar Urals. This similarity is explained by the similarity of the flora of the mountainous regions, which is characteristic of all the above-mentioned regions, due to relatively widespread species (cosmopolitan and species with a montane distribution).
A cluster analysis of the flora of the Arctic territories shows that the flora of the nearby regions of the Polar Urals, Subpolar Urals, and Nenets AO, which are close in climatic and geological conditions, are combined into one clade ( Figure 10). Figure 10. Complete graph of similarity of cyanobacterial flora in some Arctic and sub-Arctic areas (for the clustering, Sørensen index was used to show the mean distance between elements of each cluster (weighted pair group method using arithmetic averaging, numbers on ridges are similarity in percent)). FJL-Franz Josef Land Archipelago, MRt-Murmansk region tundra zone, MRf-Murmansk region forest zone, Nen-Nenets AO, NZ-Novaya Zemlya Archipelago, PU-Polar Urals, SV-Svalbard Archipelago, T-Taymyr peninsula, Y-Yamal peninsula.

Conclusions
We investigated the diversity of cyanobacteria in Ochenyrd ridge for the first time. We noted a relatively high species diversity of cyanobacteria in the northern part of the Polar Urals. In the northern part of the Polar Urals, we identified 37 species of cyanobacteria that have never before been documented in the region. A significant number of new species occurrences reflect the potentially high diversity of terrestrial cyanobacteria in this area. Such species richness is due to both many mountain habitat types and geological rock diversity. The identification of many species new to the region indicates that the potential cyanobacterial diversity of the region has not been sufficiently investigated. Based on the spatial distribution, most of the identified species are quite widespread in the Arctic and sub-Arctic. At the same time, we also found species that were not previously recorded in high-latitude regions.
The list of cyanobacteria common in the Polar Urals includes 179 species. A high similarity between the species composition of the flora in the Polar Urals and other wellstudied Arctic and sub-Arctic territories was notable. The greatest similarity was found between the flora of the neighboring region of the Nenets AO, including the assemblages of the Bolshezemelskaya tundra and the Malozemelskaya tundra.