History of the <Emphasis Type="Italic">Pinus sylvestris</Emphasis> and <Emphasis Type="Italic">Pinus nigra ssp. salzmanni</Emphasis> forest in the Sub-Mediterranean mountains (Grands Causses,Saint-Guilhem-le-Désert,southern Massif Central,France) based on charcoal from limestone and dolomitic deposits

Charcoal, the remains of Holocene fires recorded in natural sediments, allows a new approach to the study of forest evolution in the mountains of the Mediterranean region. The area of the Grands Causses and St Guilhem, southern Massif Central (France) played an important role in the preservation of steppic and pre-steppic ecosystems up to the middle Holocene. The present biodiversity developed recently (between 5000–3000 b.p.), which explains the persistence of typical alpine and steppic flora characteristic of these areas. From the middle Holocene on, both fire events in the Eastern areas of the Causse Méjean and grazing have contributed to creating the bald landscape characteristic of this region. Further south the present day forest of Pinus nigra ssp. salzmanni is a recent phenomenon. It was during the Middle Ages that the initial forest of Pinus sylvestris and Pinus nigra ssp. salzmanni, a heritage from the last glaciation, started to change. δ¹³C measurements were carried out and the results compared with reference material. These show that fire events are closely related to dry periods, implying climatic changes of increasing dryness after the middle Holocene climatic optimum.     

Deux nouveaux sites à traces de pas dinosauroïdes dans la Formation Dolomitique de l’Hettangien de Lozère,Languedoc-Roussillon,France

Recent ichnological studies revealed two new localities showing dinosaur footprints in the Hettangian Dolomitic Formation from the Causses Basin, southern France. The traces are reported from the northern part of the basin, in Lozère, an area where Lower Jurassic dinosaur ichnites were poorly documented. The surfaces bearing footprints are characterized by a large number of traces. The ichnites are ascribed to Grallator (Hitchcock, 1858), Dilophosauripus (Welles, 1971) and Eubrontes (Hitchcock, 1845) whose trackmakers were theropods. Although numerous tracksites were previously described in the southern part of the Causses Basin, these three ichnotaxa are for the first time observed in association into the Dolomitic Formation.     

Mitochondrial DNA inference between European populations of Tanymastix stagnalis and their glacial survival in Scandinavia

The early observation from 1914 of Tanymastix stagnalis in Norway was not repeated recently, showing a rare and restricted distribution of this species. All four sampled localities were concentrated in the same area of the Trollheimen Mountains with altitudes of 900–1244 m above sea level. In March 2002, a new population of T. stagnalis was observed at about 50 km north of Madrid at an altitude of 1350 m. In general, all habitats with T. stagnalis were fishless shallow ponds and varied in size from 1 to about 300 m². Natural variability of the global temperature is well accepted, but recent climate models have predicted increases in global average temperature. Based on the new biogeographical distribution, diurnal temperature variations, and biological evidence (inference with the analysis of mitochondria DNA), the immigration history of T. stagnalis was considered on the basis of two opposing immigration theories and in relation to the implications of global climate change. Two immigration theories, namely – the Tabula rasa and Nunatak, have prevailed in explaining the present distribution of plants and animals in Scandinavia. It was concluded that the rare occurrence of T. stagnalis in Norway fits into the Nunatak theory and that the species probably survived, at least, the last glaciation on Nunataks or coast refuges located in central northwestern Norway at Møre mountain and coast areas.     

Refugial races and postglacial colonization history of the freshwater amphipod Gammarus lacustris in Northern Europe

The systematic structure and postglacial population history of the freshwater amphipod Gammarus lacustris were explored in an allozyme survey of 65 populations across Northern Europe. A strong multilocus pattern of differentiation discriminated populations of the north‐east (north‐eastern Norway, northern Finland) from those in the west and the south (southern and central Scandinavia, Denmark, Poland). This principal division is attributed to postglacial colonization of the area by two main refugial races or lineages, one from the east (Russia), the other from the south (north‐western European continent). The strongly diverged Eastern and Western races (Nei's D= 0.3, from 22 loci) now meet in a secondary contact zone across a narrow sector of northernmost Norway. Genetic population compositions in this zone vary in a mosaic pattern, and show no evidence of reproductive incompatibility. Similar contacts of eastern and western lineages, far older than the latest glaciation, are now known from a number of taxa and they constitute a general pattern in Fennoscandian phylogeography. Within the Western Gammarus race, the populations through coastal north‐western Norway are further distinguished from those in southern Scandinavia and Denmark by a set of unique alleles at high frequencies (D = 0.12). This suggests an independent early colonization of the coastal region by another distinct stock, either along an early deglaciated coastal corridor from the south‐west, or directly from the ice‐free continental shelf off the Norwegian coast – a hypothesis that has also previously been presented for G. lacustris, and parallels controversial suggestions of local refugia for other taxa in Scandinavia. The coastal population type only later could come into contact with Gammarus invading over the mountains from the south; these two population types now smoothly intergrade. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 523–542.     

Glacial survival or late glacial colonization? Phylogeography of the root vole (Microtus oeconomus) in north‐west Norway

Aim It has been proposed that the root vole subspecies, Microtus oeconomus finmarchicus, survived the last glacial period on islands on the north‐west coast of Norway. The Norwegian island of Andøya may have constituted the only site with permanent ice‐free conditions. Geological surveys and fossil finds from Andøya demonstrate that survival throughout the last glacial maximum was probably possible for some plants and animals. In this study we aim to infer the recent evolutionary history of Norwegian root vole populations and to evaluate the glacial survival hypothesis. Methods DNA sequence variation in the mitochondrial cytochrome b gene was studied in 46 root voles from 19 localities. Location Northern Fennoscandia and north‐west Russia with a focus on islands on the north‐west coast of Norway. Results The phylogeographical analyses revealed two North European phylogroups labelled ‘Andøya’ and ‘Fennoscandia’. The Andøya phylogroup contained root voles from the Norwegian islands of Andøya, Ringvassøya and Reinøya and two localities in north‐west Russia. The Fennoscandian phylogroup encompassed root voles from the three Norwegian islands of Kvaløya, Håkøya and Arnøya and the remaining specimens from Norway, northern Sweden and Finland. Nucleotide diversity within the Andøya and Fennoscandian phylogroups was similar, ranging from 0.5% to 0.7%. Main conclusions Both our genetic data and previously published morphological data are consistent with in situ glacial survival of root voles on Andøya during the last glacial maximum. However, the level of genetic diversity observed in the extant island populations, the past periods of severe climatic conditions on Andøya and the ecology of the root vole are somewhat difficult to reconcile with this model. A biogeographical scenario involving late glacial recolonization along the northern coasts of Russia and Norway therefore represents a viable alternative. Our results demonstrate that complex recolonization and extinction histories can generate intricate phylogeographical patterns and relatively high levels of genetic variation in northern populations.     

Massive settlements of the Pacific oyster, <Emphasis Type="Italic">Crassostrea gigas</Emphasis>, in Scandinavia

The Pacific oyster (Crassostrea gigas) is an important aquaculture species world-wide. Due to its wide environmental tolerance and high growth rate, it has also become a successful invader in many areas, leading to major ecosystem changes. Low water temperatures were previously believed to restrict the establishment of Pacific oysters in Scandinavia. However, recent surveys reveal that the Pacific oyster is now established in many areas in Scandinavia. We present data on the current distribution, abundance and age-structure in Denmark, Sweden and Norway. The biomass of oysters in the Danish Wadden Sea increased from 1,056 to 6,264 tonnes between 2005 and 2007. Massive settlements were observed along the Swedish west coast in 2007, with densities >400 oysters per m⁻². In Norway, populations are established on the southern coast, and specimens have been found as far north as 60°N. The potential impacts and probable causes of this recent large-scale establishment are discussed.     

Linnaeus' Neptunea (Mollusca: Gastropoda)

Three species of the arcto-boreal, large gastropod Neptunea , described by Linnaeus in 1758 and 1771, occur in large numbers over wide areas of the inshore North Atlantic and adjacent Arctic seas and are conspicuous among Pliocene and Pleistocene molluscs in the Icelandic, North Sea, and western Mediterranean basins. Selections of lectotypes for these species from shells in the collection of the Linnean Society of London, and designations of their type localities, establish the identity of Linnaeus' neptunes and more accurately determine their geographic and geologic distribution. The geographic range of Neptunea (Neptunea) antiqua (L.), the type species, now extends from southern Norway to the northern Biscay coast of France and from the westernmost Baltic Sea to southwestern Ireland; this species also occurs in Pliocene-Holocene marine deposits in West and East Germany, Sweden, the Netherlands, England and France. Its type locality is determined to be the North Sea. N. (Neptunea) despecta (L.) lives in the eastern Canadian Arctic, off southern Greenland, the Barents Sea, and North Atlantic as far south as Massachusetts and Portugal; it also occurs in Pliocene-Holocene strata of eastern Canada, east-central Greenland, Norway (including Svalbard), the Soviet Union, Sweden and England. Its type locality is determined to be the postglacial deposits at Uddevalla in southwestern Sweden. N. (Sulcosipho) contraria (L.) now extends from the southern Biscay coast of France to Cape Spartel, Morocco; this species also occurs in Pleistocene and lower Holocene sequences of the western Mediterranean. Its type locality is determined to be Vigo Bay, Spain. A closely related fossil species, N. (S.) angulata (S. V. Wood), occurs in Pliocene and Pleistocene deposits of the North Sea basin.     

Southern Scandinavian lowland populations of Rhytidium rugosum (Hedw.) Kindb. (Bryophyta,Rhytidiaceae) differ significantly from those in the mountains

Abstract

Haplotype diversity patterns based on internal transcribed spacer (ITS) and gpd (glyceraldehyde 3-phosphate dehydrogenase) in Scandinavian Rhytidium rugosum were compared between four populations from the mountain range and two in the southern lowlands. The mountain populations differ from the southern lowland ones in haplotype composition and the lowland ones differ from each other, suggesting different histories. A coalescent-based analysis (LAMARC) indicated immigration into the population now found in the mountains from that represented in the lowlands. Because several factors argue against such a dispersal scenario within the relatively short postglacial period, it is proposed that these migration patterns are older than the postglacial period. It is suggested that the mountain range populations immigrated from a source population either in the north-east or within Scandinavia, whereas the lowland populations are likely to represent remains of the glacial population of lowland Europe. The highest haplotype diversity in Scandinavia was found in the Gudbrandsdalen area in southern Norway. This is probably explained by the fact that this is the only region in Europe where R. rugosum regularly reproduces sexually. The lowest diversity was found on the Great Alvar on the island of Öland off the Baltic coast of southern Sweden, and is most likely a result of gradual loss of haplotypes over time.     

New Hettangian tracks from the Causses Basin (Lozère,southern France) complement the poor fossil record of earliest Jurassic crocodylomorphs in Europe

A new vertebrate ichnological assemblage is described from the Hettangian Dolomitic Formation of the Causses Basin, at Le Serre (Lozère, southern France). We report tracks that complement the poor fossil record of lowermost Jurassic crocodylomorphs in Europe. Tetradactyl pes and pentadactyl manus imprints form a unique trackway. Traces are ascribed to Batrachopus isp. and they represent the third occurrence of this ichnogenus in European Hettangian geological formations. This is the first report of Batrachopus in Hettangian deposits of the Causses Basin. The tracks share some similarities with Batrachopus deweyi previously described from the Sinemurian of the Causses Basin. Crocodylomorph tracks co-occur with tridactyl dinosaur traces assigned to Dilophosauripus williamsi and Grallator isp. The sedimentology and palaeoichnology of the tracksite indicate that the depositional environment was a tidal to supratidal flat marsh that was emerged periodically. The ichnological assemblage from Le Serre and a synthesis of ichnotaxa co-occurring with Batrachopus in the European lowermost Jurassic tracksites confirm that crocodylomorphs living in marginal-littoral palaeoenvironments were part of theropod-dominated faunas, together with ornithopods but apparently without sauropods.     

A MOLECULAR AND MORPHOLOGICAL ANALYSIS OF THE GYMNOGONGRUS DEVONIENSIS (RHODOPHYTA) COMPLEX IN THE NORTH ATLANTIC1

The Gymnogongrus devoniensis (Greville) Schotter complex in the North Atlantic Ocean was elucidated by comparative molecular, morphological, and culture studies. Restriction fragment length patterns and hybridization data on organellar DNA revealed two distinct taxa in samples from Europe and eastern Canada. Nucleotide sequences for the intergenic spacer between the large and small subunit genes of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and the adjoining regions of both genes, differed by 12.5–13.4% between the two taxa. One of the taxa, which included material from the type locality of G. devoniensis at Torbay, Devon, England, was taken to represent authentic G. devoniensis. Within this taxon, samples from Ireland, England, northern France, northern Spain, and southern Portugal showed great morphological variation, particularly in habit, but their Rubisco spacer sequences were identical or differed by only a single nucleotide. Constant morphological features included the development, from a single auxiliary cell, of the spherical cystocarp with a thick mucilage sheath that appears to be typical of Gymnogongrus species with internal cystocarps. Two life-history types were found. Northern isolates underwent a direct-type life history, recycling apomictic females by carpospores, whereas the Portuguese isolate followed a heteromorphic life history in which carpospores gave rise to a crustose tetrasporophyte. The second group of samples, from Nova Scotia and Northern Ireland, provisionally referred to as Gymnogongrus sp., showed little morphological variation. The life history in both areas consists of apomictically reproducing diploid female gametophytes and diploid crustose bisporophytes and tetrasporophytes. Rubisco spacer sequences of the samples were identical, and the plasmid previously described in the Nova Scotian samples was also present in the Northern Ireland population. This species is widely distributed in the western Atlantic, from Newfoundland to Massachusetts. In Europe, gametophytes are known only at one site, but crusts are distributed from Denmark, Scotland (and probably Norway) to France. It is very likely that this species was introduced from one side of the North Atlantic to the other by shipping during the early nineteenth century. Several morphological features are unusual within the genus but are shared with G. leptophyllus J. Agardh from the eastern Pacific Ocean, and further work is necessary to determine whether Gymnogongrus sp. and G. leptophyllus are conspecific.     

Temperature responses of some North AtlanticCladophora species (Chlorophyceae) in relation to their geographic distribution

The temperature responses for growth and survival have been experimentally tested for 6 species of the green algal genusCladophora (Chlorophyceae; Cladophorales) (all isolated from Roscoff, Brittany, France, one also from Connecticut, USA), selected from 4 distribution groups, in order to determine which phase in the annual temperature regime might prevent the spread of a species beyond its present latitudinal range on the N. Atlantic coasts. For five species geographic limits could be specifically defined as due to a growth limit in the growing season or to a lethal limit in the adverse season. These species were: (1)C. coelothrix (Amphiatlantic tropical to warm temperate), with a northern boundary on the European coasts formed by a summer growth limit near the 12°C August isotherm. On the American coasts sea temperatures should allow its occurrence further north. (2)C. vagabunda (Amphiatlantic tropical to temperate), with a northern boundary formed by a summer growth limit near the 15°C August isotherm on both sides of the Atlantic. (3)C. dalmatica, as forC. vagabunda. (4)C. hutchinsiae (Mediterranean-Atlantic warm temperate), with a northern boundary formed by a summer growth limit near the 12°C August isotherm, and possibly also a winter lethal limit near the 6°C February isotherm; and a southern boundary formed by a southern lethal limit near the 26°C August isotherm. It is absent from the warm temperate American coast because its lethal limits, 5° and 30°C, are regularly reached there. (5) Preliminary data forC. rupestris (Amphiatlantic temperate), suggest the southeastern boundary on the African coast to be a summer lethal limit near the 26°C August isotherm; the southwestern boundary on the American coast lies on the 20°C August isotherm. For one species,C. albida, the experimental growth and survival range was wider than expected from its geographic distribution, and reasons to account for this are suggested.Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April, 1984 at the Department of Marine Biology, University of Groningen (The Netherlands). Convenor: C. van den Hoek.     

Cinematographic Observation on spore and Elater Discharge in Lophocolea

Abstract

The hepatic Plagiochila norvegica has been found in a calcareous wood in southern England. This its fourth known locality, the other three being in southern and western Scandinavia. P. norvegica is related to P. porelloides, but differs in its conspicuously dentate leaves with a bilobed apex.     

A phylogeographic analysis of Viola rupestris: three post-glacial immigration routes into the Nordic area?

Morphology and isoenzyme patterns support the taxonomic delimitation of two subspecies of Viola rupestris F. W. Schmidt in the Nordic area, i.e. ssp. rupestris and ssp. relicta Jalas. Three different, geographically distinctly defined genotypes, are revealed (based on seven enzyme systems): one in north Scandinavia (= ssp. relicta , distinct in AAT-I, AMP-I and PGM-3), one in north Finland (distinct in AMP-2), and one widespread in the southern and central parts of Norden. Two of the three unique bands in ssp. relicta are also detected in British material. The data are consistent with the scenario of three post-glacial immigration routes into the Nordic area: one from the south-west, today represented by the north Scandinavian populations, one from the east, today represented by the populations in the Kuusamo area of north Finland, and one from the south-east, today represented by widespread populations south of the mentioned areas.     

RearingTetrastichus gallerucae [hymenoptera: Eulophidae] for biological control of the ELM leaf beetleXanthogaleruca luteola

Tetrastichus gallerucae (Fonscolombe) was collected in southern France in 1985 and is being reared at the Division of Biological Control in Albany, Ca for use against the elm leaf beetle (ELB),Xanthogaleruca luteola (Müller) in northern California. This egg parasitoid can be reared easily by keeping the beetle eggs on a moist substrate to prevent desiccation and by inhibiting the growth of mold with air currents. A laboratory colony of ELB adults provides a constant supply of fresh eggs for the parasitoids. In 1985 and 1986 over 80,000T. gallerucae were released at 17 sites.      

The extent and meaning of hybridization and introgression between Siberian spruce (Picea obovata) and Norway spruce (Picea abies): cryptic refugia as stepping stones to the west?

Boreal species were repeatedly exposed to ice ages and went through cycles of contraction and expansion while sister species alternated periods of contact and isolation. The resulting genetic structure is consequently complex, and demographic inferences are intrinsically challenging. The range of Norway spruce (Picea abies) and Siberian spruce (Picea obovata) covers most of northern Eurasia; yet their geographical limits and histories remain poorly understood. To delineate the hybrid zone between the two species and reconstruct their joint demographic history, we analysed variation at nuclear SSR and mitochondrial DNA in 102 and 88 populations, respectively. The dynamics of the hybrid zone was analysed with approximate Bayesian computation (ABC) followed by posterior predictive structure plot reconstruction and the presence of barriers across the range tested with estimated effective migration surfaces. To estimate the divergence time between the two species, nuclear sequences from two well‐separated populations of each species were analysed with ABC. Two main barriers divide the range of the two species: one corresponds to the hybrid zone between them, and the other separates the southern and northern domains of Norway spruce. The hybrid zone is centred on the Urals, but the genetic impact of Siberian spruce extends further west. The joint distribution of mitochondrial and nuclear variation indicates an introgression of mitochondrial DNA from Norway spruce into Siberian spruce. Overall, our data reveal a demographic history where the two species interacted frequently and where migrants originating from the Urals and the West Siberian Plain recolonized northern Russia and Scandinavia using scattered refugial populations of Norway spruce as stepping stones towards the west.     

Morphometric analyses of capsule and seed traits in Scandinavian Papaver radicatum (Papaveraceae) in relation to the bicentric distribution pattern

The bicentric distribution pattern of certain plant species in the southern and northern Scandinavian mountains has been explained in different ways. Either by refugial survival, by late-glacial immigration to the first deglaciated areas in southern and northern Norway or by a successive fragmentation of wide-distributed populations during post-glacial time — or by present-day ecological factors. Even if the bicentric distribution pattern is at least partly explained by present-day ecological conditions, the question about the origin of the bicentric distribution still remains. One way to tackle this problem, is to investigate the morphometric and/or the genetic differentiation between isolated populations of ‘bicentric’ species and its impact on the explanation of the disjunct pattern. The overall morphometric differentiation pattern in seeds and capsules was investigated in populations of Papaver radicatum, a perennial herb with a bicentric distribution in the Scandinavian mountain range. Canonical variates analysis of capsules separates the populations into two groups in accordance with their geographic origin, i.e. the regions of southern and northern Scandinavia. The differentiation pattern indicates a two-step development of the present-day distribution: first separation of the southern and northern Scandinavian occurences of older origin, then separation between populations within each region. The results from canonical variates analysis of seeds shows a weaker variation pattern with a tendency of overlapping inter-region populations. The most northerly situated populations from the southern region are grouped with populations from the northern region. The pattern of differentiation in capsules may be interpretated in terms of refugial survival or late-glacial immigration. However, the variation pattern in seeds rather points to a scenario where a widespread occurrence that previously ranged from southern to northern Scandinavia was successively fragmented, which makes a postglacial development of the differentiation pattern more probable.     

Metazoan parasites as biological tags for stock discrimination of whitemouth croaker Micropogonias furnieri

Examination of 248 adult specimens of whitemouth croaker Micropogonias furnieri from five localities along the Brazilian coast revealed 8735 parasites belonging to 41 metazoan species. Samples from Ceará to Bahia and Rio de Janeiro to Santa Catarina showed a high level of correct assignation (92 and 87%, respectively) and cross assignation (i.e. almost all specimens misidentified in Ceará were assigned to Bahia and almost all specimens misidentified in Bahia were classified as Ceará), so samples were pooled in the northern and south‐eastern samples, and Rio Grande do Sul was considered a southern area. Eight parasite species were characteristic of the northern localities, five species were found just in the area associated with south‐eastern localities and two species were characteristic of the southern area providing first evidence of stock discreteness. The multivariate discriminant analysis successfully discriminated three groups of localities associated with three stocks of M. furnieri in Brazil: a northern stock associated with Ceará and Bahia, a south‐eastern stock related to Rio de Janeiro and Santa Catarina and a southern stock in the area of Rio Grande do Sul, which could be considered as the northern limit of the stock associated with the Common Fishing Zone of Uruguay and Argentina.     

Vegetation and ecological characteristics of the northernmost salt marshes of the European continent

We surveyed 17 locations of salt marshes along the Barents Sea coast in northern Norway (Finnmark, Nordkinnhalvøya and Varangerhalvøya), where 86 phytosociological relevés were recorded and analyzed. Two main vegetation groups were identified: Caricion glareosae and Puccinellion phryganodis, both alliances belonging to the class Juncetea maritimi, order Puccinellietalia phryganodis. The first, Caricion glareosae (upper marshes) is subject to shorter‐term flooding and is saturated by brackish water in river estuaries on sandy or sandy gravel soils. Four units were distinguished: Festuceto‐Caricetum glareosae, Caricetum mackenzie, Caricetum salinae and the Plantago maritima × borealis community. The second group (lower marshes on fine muddy surface, higher salinity, inundated for a longer period directly by the sea) belongs to the alliance Puccinellion phryganodis which encompasses two units: the associations Caricetum subspathaceae and Puccinellietum phryganodis. The floristic composition and habitat preferences of each vegetation cluster are described and our study revealed that there are no significant differences in the vegetation composition of salt marshes beyond the Arctic line and the southern subarctic sites. The observed variations are related to the geomorphology of the sites rather than to their latitude. The comparison of historical records with our recent data demonstrates the great stability of habitat conditions and species composition. The salt marshes studied meet all criteria of good quality and we found no evidence for any threatening trends like those seen in most other habitats in Europe.     

Essential oil polymorphism of Thymus praecox subsp. arcticus on the British Isles

The essential oils of 732 individual plants of Thymus praecox Opiz subsp. arcticus (E. Durand) Jalas (syn. T. drucei Ronn.) collected in Scotland, Ireland, and in the south of England have been analysed by gas chromatography (GC) and mass spectrometry (GC–MS) in order to elucidate the chemical character of this subspecies on the British Isles. In total, 69 components were identified, most of them monoterpenoids and sesquiterpenoids with hedycaryol, linalyl acetate, linalool, the germacradienols, trans-nerolidol, T-cadinol, and β-caryophyllene being the most important compounds. The analysis of the quantitative essential oil data by means of neural networks revealed that T. praecox subsp. arcticus growing in Britain is highly polymorphous. There were 17 chemotypes with the hedycaryol chemotype as the most frequent (24% of the plants), followed by the linalool/linalyl acetate chemotype (22% of the plants) and germacra-1(10),4-dien-6-ol chemotype (18% of the plants). It seems that each part of the British Isles has its special chemotype pattern with 13 chemotypes in Scotland, 11 in Ireland, and 17 in the south of England. An overview of the North Atlantic region of Europe revealed that the polymorphism of T. praecox subsp. arcticus in the essential oil is more distinctive in the southern than in the northern regions, with only 2, 5, and 1 chemotypes in Greenland, Iceland, and Norway, respectively.