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Major habitat types of Attu Island: A-view from eastern Attu Island of the snowbed-rich Attu Mountain area, 18.09.2002. Convex ridge landforms are dominated by dwarf-shrubs and concave depressions are dominated by graminoid and forb meadows. B-view from a fellfield on Gilbert Ridge, Attu Island, looking southeast along West Massacre Valley toward Massacre Bay, 18.09.2002. Terrible Mountain (elevation ca. 610 m) is on the right with Coast Artillery Hill (elevation 168 m) and Lake Elwood in the distance. The valley plain is dominated by mires of Lyngbye sedges and tall cottongrass. C-view southwest from Peaceful River toward Kingfisher Creek in the Weston Mountains (elevation ca 488 m), Attu Island, Alaska, 13.09.2002. Forb meadows dominate riparian sites and sedge mires occupy the toe slopes of the mountains. Mountain slopes are covered with a mosaic of meadows and dwarf shrub communities. D-view of the north slope of Gilbert Ridge (elevation ca 460 m) above Lake Nicolas in Siddens Valley, Attu Island, Alaska, 21.09.2002. Soils are typically saturated
Source publication
The liverwort flora of Attu Island, the westernmost Aleutian Island in the United States, was studied to assess species diversity in the hyperoceanic sector of the northern boreal subzone. The field study was undertaken in sites selected to represent a spectrum of environmental variation, primarily within the eastern part of the island. Data were a...
Contexts in source publication
Context 1
... sought to collect from a spectrum of habitats from sea shore to mountain summits (Fig. 3); these habitats included rocky and sandy shores, beach meadows and dunes, mesic forb and graminoid meadows, fern meadows, dwarf shrub heaths, alpine fellfields, mires, ponds and streams, snowbeds, rock cliffs and crevices. For each species we estimated commonness using the classes of Hickman (1993): (1) abundant; very likely to be ...
Context 2
... sought to collect from a spectrum of habitats from sea shore to mountain summits (Fig. 3); these habitats in- cluded rocky and sandy shores, beach meadows and dunes, mesic forb and graminoid meadows, fern meadows, dwarf shrub heaths, alpine fellfields, mires, ponds and streams, snowbeds, rock cliffs and crevices. For each species we es- timated commonness using the classes of Hickman (1993): (1) abundant; very likely to be encountered; nearly always found in appropriate habitats, sometimes forming dense stands; (2) common; likely to be encountered; (3) uncom- mon; unlikely to be encountered and sometimes not pres- ent in appropriate habitats; and (4) rare; extremely unlikely to be encountered, often not present in appropriate habi- tats, and often restricted to a small number of ...
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Citations
... However, given the limited material available from the Commander Islands, it may be that we failed to identify some traits that could be considered environmentally induced and which could correlate with genetic differences. In addition, the lack of information on the distribution of Scapania umbrosa in the Aleutian Islands is not at all proof of the real absence of the species there, given the fragmentary data on the flora of Aleutian liverworts in general [46,47]. Thus, both of the following are equally probable: the distribution of the Alaskan and Commander haplotypes in the Aleutian Arch; and the distribution of only one (identified by us) haplotype, which may be connected by transitions with the haplotype known from Alaska, or may not be connected with it by the transitions. ...
... It is interesting that the species is not yet known in the Aleutians [46,47], although such findings of the species seem logical and expected; given the modern distribution of the species, it is logical to assume that it could migrate to Bering Island from Alaska through the Aleutian chain. Additionally, birds could be considered possible agents for reaching the island. ...
The distribution of liverworts in the North Pacific is still poorly understood. Scapania umbrosa, which is rare in Asia, was first recorded during the study of the liverwort flora of the Commander Islands (the westernmost Aleutians). The results of the molecular genetic analysis not only confirmed that the specimen belonged to Scapania umbrosa but also demonstrated the genetic specificity of the discovered population in comparison with the European, Siberian, and Alaskan populations. The island population of Scapania umbrosa is likely a recently diverged isolate of the species. Previously reported data on the distribution of Scapania umbrosa in the Russian Far East from Kamchatka and Kunashir (VBGI Herbarium), as well as from Sakhalin and Southern Primorye (reported in GBIF), are based on misidentifications. Morphological descriptions, distinguishing characters, line drawings, and photographs of Scapania umbrosa based on the collected material are provided.
... The dominate climate type in all those regions is Warm-summer Mediterranean (Beck et al., 2018), thus the same as mentioned above for the British Columbia occurrence of the species. The climate of Aleutians is classified by the ecoclimatic-phytogeographical system of Tuhkanen (1984, original not seen, cited after Talbot et al., 2018) as northern boreal, hyperoceanic, and perhumid. Unlike to the latter, the Köppen-Geiger climate classification cited above refers climate in the western Aleutians (westward of Unalaska) to Subpolar Oceanic Climate type. ...
Gyrothyra underwoodiana is the only species of a peculiar monotypic family, a remarkable western North American endemic. Recent exploration has revealed Gyrothyra at the western end of the Commander-Aleutian Island Chain (Bering Island), and this is the first record of the taxon in Russia. The species was collected in four localities in various parts of the island and these findings formally emphasizes the West-North American connections of the flora of the Commander Islands. However, the distribution patterns of Gyrothyra in other Aleutians may suggest the adventive character of occurrence of the species on Bering Island. The morphological description and illustrations of G. underwoodiana based on specimens from Bering Island, as well as discussion on its ecology, morphology and distribution are provided.
... An illustrative comparison can be done with the adjacent areas that are relatively well-studied: the Paramushir Island liverwort flora (with a clearly hemiarctic vegetation) includes 85 species [40]. Attu Island, situated in a similar zone, counts 112 species [41]. However, these islands are located in a hemiarctic vegetation zone. ...
... The data on taxonomic diversity and area size in selected floras used for graphic diagram presented in Figure 1. The data on diversity are from [36][37][38][41][42][43][44] and the present paper. The data on the area are from https://en.wikipedia.org/wiki/Main_Page, ...
The long coexistence of various floral elements, landscape diversity, and island isolation led to the formation of the richest Eurasian hemiboreal liverwort flora in the southern Kurils. This land that covers less than 5000 square kilometres and houses 242 species and two varieties of liverworts and hornworts. The flora ‘core’ is represented by hemiboreal East Asian and boreal circumpolar taxa. Other elements that have noticeable input in the flora formation are cool-temperate East Asian hypoarctomontane circumpolar and arctomontane. The distribution of some species is restricted to the thermal pools near active or dormant volcanoes or volcanic ash deposits; such species generally provide specificity to the flora. Despite the territorial proximity, the climate of each considered island is characterized by features that, in the vast majority of cases, distinguish it from the climate of the neighbouring island. The last circumstance may inspire the difference in the liverwort taxonomic composition of each of the islands. The comparison of the taxonomic composition of district floras in the Amphi-Pacific hemiarctic, boreal, and cool-temperate Asia revealed four main focal centres: East Kamchatka Peninsula and Sakhalin Island, the southern Sikhote-Alin and the East Manchurian Mountains, the mountains of the southern part of the Korean Peninsula, and the South Kurils plus northern Hokkaido. The remaining floras involved in the comparison occupy an intermediate position between these four centres.
... However, it easily penetrates north ward to the Anyui River (49°N), Komsomol'sky State Na ture Reserve (51°N), and northwestward to the Tu ku ring ra Range (~54°N), and unexpectedly appears in the Com man der Islands (Mednyj Island at almost 55°N), al though it does not occur on the Kamchatka Peninsula. The dist ri bu tion in the Commanders may be relictual, like many liver wort taxa in the Aleutian Chain (Talbot et al. 2018) (Fig. 2: 8). Description. ...
