Ice-free Refugia Research Articles

Mitochondrial DNA structuring of Antarctic prions (Pachyptila desolata, Procellariidae)

Prions (Pachyptila) are small seabirds with a Southern Hemisphere breeding distribution. Antarctic prion (Pachyptila desolata) and Salvin’s prion (P. salvini) are two species that are regularly recorded in New Zealand as beach-wrecks but they are difficult to distinguish morphologically. Salvin’s prion is restricted to breeding on the Prince Edward Islands and Crozet Islands in the Indian Ocean but Antarctic prions have a circumpolar breeding distribution on numerous sub-Antarctic and Antarctic islands in the Southern, South Atlantic and Indian Oceans. Our aim was to examine the level of mitochondrial DNA (mtDNA) structuring within Antarctic prion and Salvin’s prion colonies, to test whether this technique can determine the provenance of beach-cast birds. The Auckland Islands Antarctic prion population exhibited distinct mtDNA haplotypes from all other populations, supporting the suggestion that these islands may have been an ice-free refugium during the Last Glacial Maximum. All other sampled breeding populations shared haplotypes, limiting the use of these sequences for determining the provenance of beach-cast birds. None of our museum specimens of Salvin’s prion collected from breeding colonies produced DNA sequences. This result indicates that the method by which these specimens, which were collected in the 1960s and 70s, were preserved, or subsequent treatments, has resulted in the loss of their DNA.

Ancient bears provide insights into Pleistocene ice age refugia in Southeast Alaska.

During the Late Pleistocene, major parts of North America were periodically covered by ice sheets. However, there are still questions about whether ice-free refugia were present in the Alexander Archipelago along the Southeast (SE) Alaska coast during the last glacial maximum (LGM). Numerous subfossils have been recovered from caves in SE Alaska, including American black (Ursus americanus) and brown (U. arctos) bears, which today are found in the Alexander Archipelago but are genetically distinct from mainland bear populations. Hence, these bear species offer an ideal system to investigate long-term occupation, potential refugial survival and lineage turnover. Here, we present genetic analyses based on 99 new complete mitochondrial genomes from ancient and modern brown and black bears spanning the last ~45,000 years. Black bears form two SE Alaskan subclades, one preglacial and another postglacial, that diverged >100,000 years ago. All postglacial ancient brown bears are closely related to modern brown bears in the archipelago, while a single preglacial brown bear is found in a distantly related clade. A hiatus in the bear subfossil record around the LGM and the deep split of their pre- and postglacial subclades fail to support a hypothesis of continuous occupancy in SE Alaska throughout the LGM for either species. Our results are consistent with an absence of refugia along the SE Alaska coast, but indicate that vegetation quickly expanded after deglaciation, allowing bears to recolonize the area after a short-lived LGM peak.

The past, present, and future of the Siberian Grouse (Falcipennis falcipennis) under glacial oscillations and global warming

Global climate change has a significant effect on species, as environment conditions change, causing many species' distributions to shift. During the last three million years, the earth has experienced glacial oscillations, forcing some species to survive in ice-free refugia during glacial periods and then disperse postglacially. In this study, by assessing the potential distribution of Siberian Grouse (Falcipennis falcipennis), we used Global Circular Models and Representative Concentration Pathways to model their pattern of range changes during glacial oscillations and the potential impact of present global warming. We used 158 location records of Siberian Grouse to generate a full climate model using 19 bioclimate variables in MaxEnt. We discarded variables with a correlation coefficient larger than 0.8 and relatively lower modeling contributions between each pair of correlated variables. Using the remaining variables, we created a normally uncorrelated simple climate model to predict the possible distribution of Siberian Grouse from the most recent Ice Age to present and to 2070. Then we added geographical data and the human interference index to construct a multiple factor full model to evaluate which were important in explaining the distribution of Siberian Grouse. The Total Suitability Zone (P ​≥ ​0.33) of Siberian Grouse is about 243,000 ​km2 and the Maximum Suitability Zone (P ​≥ ​0.66) is 36,000 ​km2 and is confined to the Russian Far East. Potential habitat modeling suggested that annual precipitation, annual mean temperature, and the distance from lakes are the most explanatory variables for the current distribution of Siberian Grouse. The distribution center moved to the southeast during the Last Glacial Maximum and spread back to the northwest after the ice melted and temperatures rose. The total area range of Siberian Grouse experienced a dramatic loss during the Last Glacial Maximum. Global warming is presently forcing the Siberian Grouse to migrate northward with a contraction of its range. There is an urgent need to protect its habitat, because little of its Maximum Sustainable Zone is protected, although there are some large reserves in that area.

Происхождение гольцовых пустынь Европейской Арктики: обзор теорий.

The main theories of origin of the European Arctic tundra and subarctic mountain(goltzy)deserts are reviewed, in application to the Kola Peninsula. The theory of «tabula rasa» stated that all plants died during glaciation, and then immigrated fromtheCentral Europe, Siberia, and British Isles. According to another theory, during several Pleistocene glaciations, plants survived in ice-free refugia. Modern bota-ny point of views supports post-glacial migration of species and rather «tabula rasa»theory. The border of the timberline moving up inthe Holocene thermal optimum did not affect the subarctic mountain de-serts, unlike the tundra zone. Based on this, the evolution of the high mountain deserts vegetation probably meant the establishment of groups of species that differ from modern communities of the lower disposed tundra zone. Many types of mountain tundra vegetation, apparently, came from the mountains of North-East Azia; however, many species have been originated from the forest communi-ties. The subarctic mountain deserts have apparently not changed since the retreat of the glacier.

Origin of a divergent mtDNA lineage of a freshwater snail species, Radix balthica, in Iceland: cryptic glacial refugia or a postglacial founder event?

The biogeography of Iceland is controversial. Some authors believe that all Icelandic life originated after postglacial dispersal events (tabula rasa hypothesis), but others assume that some organisms survived the last glaciation in ice-free refugia. To extend existing knowledge of the freshwater biogeography of Iceland, we used a snail species, Radix balthica, as a model system. Based on a sample of 1,070 sequences of the cytochrome c oxidase subunit I gene from Iceland and from islands of the British Isles and continental Europe, a distinct Icelandic lineage was discovered. To explain the origin of the Icelandic lineage, two alternative scenarios were proposed: (i) postglacial colonization followed by rapid divergence under an elevated mutation rate and (ii) ancient preglacial colonization with survival during multiple glacial events in geothermal refugia and slow divergence under a ‘standard’ mutation rate. The results of neutrality tests and mismatch analyses and the star-like shape of the network indicated a recent population expansion of this species in Iceland. The modeling results within an approximate Bayesian computation framework supported the tabula rasa scenario. Based on our findings, a Holocene origin for the Icelandic lineage of R. balthica was suggested, which evolved under a mean rate of 7.95 × 10−7 substitutions/site/year.

Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate.

Past glaciation events have played a major role in shaping the genetic diversity and distribution of wild sheep in North America. The advancement of glaciers can isolate populations in ice-free refugia, where they can survive until the recession of ice sheets. The major Beringian refugium is thought to have held thinhorn sheep (Ovis dalli) populations during times of glacial advance. While isolation in the major refugium can account for much of the genetic and morphological diversity seen in extant thinhorn sheep populations, mounting evidence suggests the persistence of populations in smaller minor refugia. We investigated the refugial origins of thinhorn sheep using ~10000 SNPs obtained via a cross-species application of the domestic sheep ovine HD BeadChip to genotype 52 thinhorn sheep and five bighorn sheep (O. canadensis) samples. Phylogenetic inference revealed a distinct lineage of thinhorn sheep inhabiting British Columbia, which is consistent with the survival of a group of thinhorn sheep in a minor refugium separate from the Beringian refugium. Isolation in separate glacial refugia probably mediated the evolution of the two thinhorn sheep subspecies, the white Dall's sheep (O. d. dalli), which persisted in Beringia, and the dark Stone's sheep (O. d. stonei), which utilized the minor refugium. We also found the first genetic evidence for admixture between sheep from different glacial refugia in south-central Yukon as a consequence of post glacial expansion and recolonization. These results show that glaciation events can have a major role in the evolution of species inhabiting previously glaciated habitats and the need to look beyond established refugia when examining the evolutionary history of such species.

Islands in ice: isolated populations of Cryptopygus sverdrupi (Collembola) among nunataks in the Sør Rondane Mountains, Dronning Maud Land, Antarctica

Molecular variation among Antarctic Collembola has been well appreciated over the last decade. The majority of studies have focussed on the Transantarctic Mountains and Antarctic Peninsula, and more recently Dronning Maud Land, which now accounts for all known continental species. Within most species, mean mitochondrial DNA (mtDNA) sequence divergence has not been more than around 2%, but in 2010 far greater levels of infraspecific sequence divergence (9.2–10.9%) were discovered in three species: Friesea grisea (10.2%), Gressittacantha terranova (10.4%) and Cryptopygus antarcticus (9.2%). Here, we present the first phylogeographic study on Cryptopygus sverdrupi from Dronning Maud Land. We found that mtDNA COI and 16S haplotypes clustered into two lineages with a mean COI sequence divergence of around 7.1%. The mixing of haplotypes between nearby nunataks separated by up to 15 km revealed support for ongoing (but rare) dispersal, although a single site, the most geographically isolated (by 40–58 km) was also the most genetically divergent. These levels of sequence divergence indicate persistence of biota throughout the Miocene and Pliocene isolated in glacial refugia. Expanding sampling of C. sverdrupi from additional ice-free refugia throughout Dronning Maud Land will be important to further our understanding of the evolutionary processes that have influenced the Antarctic continent, its landscape and biota.

Could brown bears (Ursus arctos) have survived in Ireland during the Last Glacial Maximum?

Brown bears are recorded from Ireland during both the Late Pleistocene and early–mid Holocene. Although most of the Irish landmass was covered by an ice sheet during the Last Glacial Maximum (LGM), Irish brown bears are known to have hybridized with polar bears during the Late Pleistocene, and it is suggested that the Irish brown bear population did not become extinct but instead persisted in situ through the LGM in a southwestern ice-free refugium. We use historical population modelling to demonstrate that brown bears are highly unlikely to have survived through the LGM in Ireland under any combination of life-history parameters shown by living bear populations, but instead would have rapidly become extinct following advance of the British–Irish ice sheet, and probably recolonized Ireland during the end-Pleistocene Woodgrange Interstadial from a closely related nearby source population. The time available for brown bear–polar bear hybridization was therefore restricted to narrow periods at the beginning or end of the LGM. Brown bears would have been extremely vulnerable to extinction in Quaternary habitat refugia and required areas substantially larger than southwestern Ireland to survive adverse glacial conditions.

Palaeoglaciology of the Alexander Island ice cap, western Antarctic Peninsula, reconstructed from marine geophysical and core data

The glacial history of the continental shelf northwest of Alexander Island is not well known, due mainly to a lack of targeted marine data on Antarctica's palaeo-ice sheets in their inter-ice-stream areas. Recently it has been argued that the region was ice-free at the Last Glacial Maximum (LGM) and thus a potential site for glacial refugia. In this paper, multibeam swath bathymetry, sub-bottom profiles and sediment cores are used to map the Alexander Island sector of the Antarctic Peninsula margin, in order to reconstruct the shelf's palaeoglaciology. Sea-floor bedforms provide evidence that an independent ice cap persisted on Alexander Island through the LGM and deglaciation. We show that this ice cap drained via two major, previously-undescribed tidewater outlets (Rothschild and Charcot Glaciers) sourced from an ice dome centred over the west of the island and near-shore areas. The glaciers grounded along deep, fjord-like cross-shelf troughs to within at least ∼10–20 km of the shelf edge, and probably reached the shelf break. Only one small outer-shelf zone appears to have remained free of ice throughout an otherwise extensive LGM. During retreat, grounding-line geomorphology indicates periodic stabilisation of Charcot Glacier on the mid-shelf after 13,500 cal yrs BP, while Rothschild Glacier retreated across its mid-shelf by 14,450 cal yrs BP. The timing of these events is in phase with retreat in nearby Marguerite Trough, and we take this as evidence of a common history and forcing with the Antarctic Peninsula Ice Sheet. The fine details of ice flow documented by our new reconstruction highlight the importance of capturing complex ice flow patterns in models (e.g. in inter-stream areas), for understanding how region-specific parts of Antarctica may change in the future. Moreover, the reconstruction shows that glacial refugia, if present, cannot have been extensive on the Alexander Island shelf at the LGM as indicated by previous biological studies; instead, we argue that any ice-free refugia were probably restricted to isolated outer-shelf pockets, that opened, closed, or were maintained through diachronous ice-sheet advance and retreat.

Glacial survival may matter after all: nunatak signatures in the rare European populations of two west-arctic species

Biogeographers claimed for more than a century that arctic plants survived glaciations in ice-free refugia within the limits of the North European ice sheets. Molecular studies have, however, provided overwhelming support for postglacial immigration into northern Europe, even from the west across the Atlantic. For the first time we can here present molecular evidence strongly favouring in situ glacial persistence of two species, the rare arctic-alpine pioneer species Sagina caespitosa and Arenaria humifusa. Both belong to the 'west-arctic element' of amphi-Atlantic disjuncts, having their few and only European occurrences well within the limits of the last glaciation. Sequencing of non-coding regions of chloroplast DNA revealed only limited variation. However, two very distinct and partly diverse genetic groups, one East and one West Atlantic, were detected in each species based on amplified fragment length polymorphisms (AFLPs), excluding postglacial dispersal from North America as explanation for their European occurrences. Patterns of genetic diversity and distinctiveness indicate that glacial populations existed in East Greenland and/or Svalbard (A. humifusa) and in southern Scandinavia (S. caespitosa). Despite their presumed lack of long-distance dispersal adaptations, intermixed populations in several regions indicate postglacial contact zones. Both species are declining in Nordic countries, probably due to climate change-induced habitat loss. Little or no current connectivity between their highly fragmented and partly distinct populations call for conservation of several populations in each geographic region.

Low genetic variation for Dendrobaena octaedra from Greenland compared to populations from Europe and North America: Refuge or selection?

Summary The genetic relationship of 345 specimens of the parthenogenetic lumbricid Dendrobaena octaedra from Greenland, Canada and Europe were analysed by means of isozymes. The results showed that populations from Greenland were markedly different from Canadian and European populations, suggesting that dispersal between Greenland and the continents has been much more restricted in the past than dispersal between North America and Europe. This observation supports to the notion that Greenland populations have persisted for a long period and perhaps have survived the last glacial period in ice-free refugia. A highly significant positive correlation was seen between diversity measured either as mean haploid diversity or clonal diversity and mean temperature of the annual coldest month. These results indicate that temperature might cause selection in colder climates or that sexual processes in D. dendrobaena could have been active recently on an evolutionary time scale.

EVOLUTIONARY HISTORY OF THE ARCTIC GROUND SQUIRREL (SPERMOPHILUS PARRYII) IN NEARCTIC BERINGIA

Pleistocene glaciations had significant effects on the distribution and evolution of arctic species. We focus on these effects in Nearctic Beringia, a high-latitude ice-free refugium in northwest Canada and Alaska, by examining variation in mitochondrial cytochrome b (Cytb) sequences to elucidate phylogeographic relationships and identify times of evolutionary divergence in arctic ground squirrels (Spermophilus parryii). This arctic-adapted species provides an excellent model to examine the biogeographic history of the Nearctic due to its extensive subspecific variation and long evolutionary history in the region. Four geographically distinct clades are identified within this species and provide a framework for exploring patterns of biotic diversification and evolution within the region. Phylogeographic analysis and divergence estimates are consistent with a glacial vicariance hypothesis. Estimates of genetic and population divergence suggest that differentiation within Nearctic S. parryii occurred as early as the Kansan glaciation. Timing of these divergence events clusters around the onset of the Kansan, Illinoian, and Wisconsin glaciations, supporting glacial vicariance, and suggests that S. parryii survived multiple glacial periods in Nearctic Beringia. Across the Arctic, Beringia has been identified as an important regional refugium for a number of species. Within Nearctic Beringia, genetic differentiation across populations of arctic ground squirrels further reflects the effect of glacial patterns on a finer scale. The arctic ground squirrel has had a long evolutionary history in the Nearctic, with strong phylogeographic structure and stable clades persisting through multiple glacial cycles.

Trans‐Atlantic dispersal and phylogeography of Cerastium arcticum (Caryophyllaceae) inferred from RAPD and SCAR markers

Cerastium arcticum is an autogamous pioneer species with a distribution limited to the North Atlantic region. It has been suggested that such species must have survived in ice-free refugia on both sides of the Atlantic throughout the last, or even several, of the Pleistocene glaciations, because they lack special adaptations for long-distance dispersal. To address the possibility for recent trans-Atlantic dispersal of C. arcticum, we analyzed random amplified polymorphic DNA (RAPD) and sequence characterized amplified region (SCAR) differentiation among 26 populations of this high-polyploid species. Three SCAR markers were obtained that verified the main patterns identified in the RAPD analysis. Eighty-four multilocus RAPD phenotypes were observed in the 126 plants analyzed, based on 35 polymorphic markers. Multivariate analyses and analyses of molecular variance (AMOVAs) identified two highly divergent groups of populations: one arctic group (western and eastern Greenland, and the archipelagos of Svalbard and Franz Josef Land) and one nonarctic group (southern and northern Norway, and Iceland), indicating that C. arcticum is composed of two lineages with different evolutionary histories. However, there was little geographic structuring within each lineage, in spite of the fact that both lineages are disjunctly distributed across the Atlantic. Occurrence of very similar, in some cases even identical RAPD multilocus phenotypes on both sides of the Atlantic in this autogamous allopolyploid is most probably caused by postglacial dispersal. The present geographic distribution of C. arcticum may thus have been established after trans-Atlantic expansion from two Weichselian refugia, one for each evolutionary lineage. Unexpectedly, the level of intrapopulational variation increased towards the north. This may reflect that interpopulational migration is most extensive in the treeless arctic environment, where the species has a more continuous distribution than in the more southerly areas.

A TEST OF THE GLACIAL REFUGIUM HYPOTHESIS USING PATTERNS OF MITOCHONDRIAL AND NUCLEAR DNA SEQUENCE VARIATION IN ROCK PTARMIGAN (LAGOPUS MUTUS).

The glacial refugium hypothesis (GRH) proposes that glaciers promoted differentiation and generation of intraspecific diversity by isolating populations in ice-free refugia. We tested three predictions of this hypothesis for the evolutionary divergence of rock ptarmigan (Lagopus mutus) during the Wisconsin glaciation of the late Pleistocene. To do this, we examined subspecies distributions, population genetic structure, and phylogenetic relationships in 26 populations across North America and the Bering Sea region. First, we analyzed sequence variation in the mitochondrial control region, in a nuclear intron (Gapdh), and in an internal transcribed spacer (ITS1). Control region sequences of 154 rock ptarmigan revealed strong population and phylogeographic structure. Variation in intron sequences of 114 rock ptarmigan also revealed significant population structure compatible with results for the control region. Rock ptarmigan were invariant for ITS1. Second, we show that five known Nearctic refugia and an Icelandic refugium are concordant with the current distribution of morphologically distinct subspecies; five of these six refugia are geographically concordant with the distribution of closely related control region haplotypes. Third, our estimates of the time since phylogenetic lineages diverged predated the last glacial maximum for all but two lineages. In addition, all lines of evidence suggest that two unknown refugia in the Bering Sea region supported rock ptarmigan during the Wisconsin glaciation. Overall, our results are most consistent with the hypothesis that isolated populations of rock ptarmigan diverged in multiple refugia during the Wisconsin and that geographic variation reflects patterns of recolonization of the Nearctic after the ice receded. The GRH may therefore offer the most plausible explanation for similar biogeographic patterns in a variety of Nearctic vertebrates.

Needle flavonoid variation in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) populations

The variability of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) populations was studied with the help of needle flavonoids. Of the two proanthocyanidins and six flavonols detected and measured by high performance liquid chromatography, myricetin and prodelphinidin allowed partial separation of the sampled coastal Douglas-fir populations into three geographical groups. Even though conspicuous differences were found between the northernmost and southernmost provenances, flavonoid markers were insufficient to identify the origin of a coastal Douglas-fir population without ambiguity. In accordance with other genetic markers, it would be inappropriate to recognize races within the sampled area of coastal Douglas-fir. From a biogenetical point of view, the synthesis of prodelphinidin appears to be governed by a gene present in two codominant allelic forms. The alleles are differently expressed from one population to another in such a way that there is a latitudinal cline of prodelphinidin throughout the sampled coastal Douglas-fir populations. The gradual decrease of prodelphinidin from south to north tends to support the idea that coastal Douglas-fir has migrated in this same direction from ice-free refugia of the Wisconsin glaciation period. To confirm the latitudinal cline and the mode of inheritance of prodelphinidin in coastal Douglas-fir, additional populations should be analyzed and segregation data from known pedigrees should be obtained respectively.Key words: Pseudotsuga menziesii var. menziesii, Pinaceae, flavonoids, geographical variation.

The origin of Arctic terrestrial and freshwater tardigrades

The tardigrade faunas of six Arctic sites (Canadian Axel Heiberg I., east and west coasts of Greenland, Iceland, Svalbard, Novaya Zemlya and the Russian Taimyr Peninsula) form, with those of northern North America, a coherent “Nearctic-Arctic” biogeographic cluster. This cluster is distinct from that of “Northern and Alpine Europe”. Few, if any, Arctic tardigrades survived Pleistocene glaciation in situ amongst ice-free refugia. Similarly, few/none moved south ahead of the advancing ice-cap into the deglaciated Palaearctic and Nearctic and subsequently returned north during the Holocene deglaciation. It is more probable that most Arctic tardigrades are derived from wind-blown Nearctic propagules that colonized the region during the Holocene.

Native American Biological Diversity and the Biogeographic Influence of Ice Age Refugia

The Wisconsin glaciation divided North America into a number of ice-free refugia for flora and fauna. Pat- terns of variation of certain North American mammalian species have been interpreted as a product of biological dif- ferentiation arising from isolation in these refugia. Recent- ly, a tripartite biological and linguistic division of human populations in North America has been proposed by a number of researchers. The tripartite division in biological and linguistic traits correlates with three ice-free refugia that existed during the Wisconsin. These refugia would have provided the necessary isolation for the development of biologically and linguistically divergent groups. The human data can be seen as part of a broader pattern of glacial influences on biological variation among North American mammals.

A sidelight on the geography in Norway 1889

An article by one of the pioneers of the Norwegian Geographical Society, the geologist Hans Reusch, demonstrates how skilled observations in the landscape a hundred years ago produced important ideas. In recent years, however, new knowledge has effected some of the theories which were based upon these ideas. The fate of the theory of ice-free refugia during the Ice Age in Scandinavia should demonstrate how recent research in various sciences effected a theory based upon ideas proposed a hundred years ago.

Pollen and spores transport into the Antarctic

Pollen deposition in a 7 cm thick moss turf (Polytrichum juniperinum) from a site in Admiralty Bay (King George Island, maritime Antarctic zone) and in three cushions of Schistidium antarcticum (1–3 cm thick) from Bailey and Clark Peninsula (Wilkes Land, Greater Antarctica) were investigated. Twenty-four pollen and spore taxa were identified from a total of 1094 grains in the sample from Admiralty Bay. By contrast, the 3 samples from Wilkes Land contained only 10 grains (5 taxa). While the former sample was poor in lichen-mycobiont spores the latter revealed very many. Pollen deposition appears to be a good indicator of direction and frequency of immigration of cryptogamic propagules. It seems that the presence of cryptogamic species in the maritime Antarctic zone is predominantly the result of long-distance transport from neighbouring South America and a selection by climatic factors. The low frequency of pollen in Wilkes Land indicates a separation of this part of Antarctica from propagule exchange with other continents and the cryptogams of most of the Antarctic continent may represent a largely relictual flora which survived in ice-free refugia.

Twenty-Eight Bryophytes New to Svalbard

Localities and notes on ecology, distribution and taxonomy are given for three hepatics and twenty-five mosses new to the Svalbard ar- chipelago, Norway, European Arctic. A lectotype is selected for Tetrapolodon pallidus Hag. This paper is the first in a series to deal with the bryophyte flora of Svalbard. The papers will take up problems concerning taxonomy, nomenclature, ecology, geography and history. One of the tasks will be to revise old collections preserved in Scandina- vian herbaria. Finally the intention is to write an annotated list of the bryophytes of Svalbard. In the summers of 1973 and 1974 I visited Svalbard, partly to collect mosses. Both years I took part in an expedition from the University of Trondheim. The first year we stayed at Kapp Wijk in Isfjorden, and the second year in Ny-Alesund, Kongsfjorden and in Liefdefjorden. The visits lasted for about two months each year (25 June-25 Au- gust). Localities referred to in this paper are shown in Figure 1. Unless otherwise stated, the bryophytes were collected in 1974. A considerable amount of material was brought home, and only parts of it have been worked up. But it can already be said that the collections will add much to our knowledge about the bryophyte flora of Svalbard. Many species are reported for the first time from the Archipelago, and several species reported in the literature as rare or very rare have been found to be rather widespread. The island Bjornoya is not re- garded as a part of Svalbard in this work. Species reported as new to Svalbard in this paper will also be of great importance from a bryogeographical point of view. Some authors have claimed that there must have been ice free refugia on Svalbard during the last Ice Age. The reason for this has been the existence of a small endemic group of taxa of vascular plants (Ronning, 1965a) and a larger group of lichens (Lynge, 1938). In North America the existence of such refugia is demonstrated by geological methods, and both vascular plants and bryophytes are used in the delimitation of the refugia (see e.g. Schofield, 1972; Steere, 1976). The bryophytes have turned out to be more useful than expected. Vitt (1976) found that several species of the genus Seligeria in North America occur only in the vicinity of either unglaciated areas or in areas hypothesized as plant refugia; S. oelan-