Arcto-alpine disjunction

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Silberwurz on the southern edge of the area on the Velika Jastrebica in the Orjen Mountains. The arctic-alpine glacial relic inhabits periglacial locations

Arctic-alpine disjunction is a noticeable division of a group of animals and plants that occurs in habitats of the tundra or cold steppes, on the one hand in high mountains of the temperate zone (less often subtropical- Mediterranean mountains) and on the other hand in the Arctic . In the two sub-areas, which are separated from one another by a wide gap in the Central European-Eastern European flat and hill country, a large number of the same species occur. This distribution pattern mostly goes back to an area of ​​the cold-loving species that was formerly contiguous in the Ice Age , which has been reduced in size by the warming that has occurred since then and split up into sub-areas. The occurrence of animals and plants in isolated, small habitats , such as individual mountain peaks, should then be understood as glacial relics of the Ice Ages. The area type, which has been thoroughly investigated in both geobotanical and zoogeographical literature, as well as phylogenetically , is to be found primarily in Eurasia , as the great mountain ranges run latitudinally from west to east and flatlands also predominate between the arctic and temperate regions. In North America, the arcto-alpine disjunction does not occur, as the mountain ranges predominantly run longitudinally and boreal coniferous forest grew in the immediate vicinity of the Laurentine Ice Sheet during the maximum freezing phase .

Climate history

Ice age maximum of the last two glacial periods in Europe: Weichsel / Würm complex and Saale / Riß complex. Most of the European lowlands between Europe, Siberia and Alaska - the latter two were connected by the Bering Land Bridge - remained unglaciated. The climate was dry and cold. The vegetation consisted of a mixture of northern and continental floral elements from alpine, arctic-alpine, arctic, sub-arctic, northern montane and southern, northern and widespread continental species

The commonality of the area shape in different groups of living beings can be traced back to a common climate-historical background. Since there is a positive correlation between the extent of the Palearctic , Eurasian and Holarctic subareas for many species groups , there must have been a zonal spread in the past . This is explained by the extent of the periglacial areas in the Pleistocene , which formed a coherent large landscape between the Atlantic and the Pacific during the glacial periods . In the ice ages, which lasted more than a million years, at least six glacial phases with decreasing temperatures had an impact on the growth of the ice masses as well as on processes of landscape dynamics, such as the formation of permafrost and widespread appearance of periglacial areas. This also had strongly regressive effects on the previously existing vegetation.

The evidence of arctic-alpine elements in the temperate and meridional mountain ranges, along with quaternary geological evidence, formed one of the decisive arguments for the thesis that inland ice and ice caps had led to the retreat of the arctic-tertiary vegetation (including Persian ironwood or Zelkova ). After their withdrawal, suitable living conditions were found and settled both in the far north and in higher mountain regions. The mass occurrence of dryas (silver arum) is taken as the leading species of the arctic-alpine flora . With the fossil deposits of dryas between southern and central England, Brittany, the Benelux countries, central and eastern Europe and central Russia, the extent of the former cold-age tundra in Europe can be reconstructed.

Exchange of flora and fauna

Pointed keels have their center of diversity in the Arctic. Relics from southern regions form pairs of species such as the Dinaric pointed keel to the Alpine pointed keel
The caterpillars of the thick-headed butterfly Pyrgus centaureae live on the cloudberry , which in Europe is mainly a glacial relic of the far north

During the ice ages, the arcto-tertiary stock of forms was almost completely eliminated, and the forest and high mountain flora were pushed back into refuge areas. On the other hand, the exchange of flora with other mountains and the northern regions was considerably intensified. Arcto-alpine species are distributed from the Picos de Europa in northern Spain to the Japanese Alps .

An example of a Eurasian-American-Arctic species is the Alpine Apollo , whose European sub-area only includes the central Alps. Not until the Urals did he settle in Siberia, Mongolia, Alaska, Canada and the western USA to New Mexico. However, it is missing in Europe in Scandinavia or Iceland. Not all of the cold-age species were able to form an arctic-alpine area. A large part of the tundra species only colonizes one of the sub-areas and is thereby separated into alpine or arctic clan pairs. Examples of the clan pairs divergent between the Arctic and temperate alpine high mountains are Salix retusa - Salix polaris , or Oxytropis dinarica - Oxytropis campestris .

The same pattern can be found in the fauna of the Palearctic . Several areas of arctic-alpine disjunction can also be described. There are distribution areas between European and Asian high mountains and the Arctic or those that only include one of the high mountain systems and the Arctic. Cases of purely European arcto-alpine disjunction are rarer. The following butterflies have a European arctic-alpine area: Pyrgus andromedae or Pygmaeana fusca . In Asia, however, it includes more species: u. a. Pyrgus centaureae , Colias hecla , Euphydras iduna , Boloria alaskensis or Oeneis bore . The Siberian arctic-alpine sub-area includes the Altai and Sajan as well as the Siberian Arctic. Even with butterflies there are clan pairs that can be separated into arctic and alpine forms. The southernmost limit of distribution of such alpine species with closely related arctic ones is in the high mountains of the Balkan Peninsula. They are: Agriades glandon - Agriades aquilo , Colostygia lineolata - Colostygia turbata , Holoarctia cervini - Holoarctia puengeleri u. a.

Due to the reproductive isolation of the highly fragmented occurrences of individual high mountains, numerous arcto-alpine species have often formed subspecies that only emerged through geographical separation after the Ice Ages . Even among these, there are only disjunctions between the mountains and landscapes lying in the same zonobiom . This type of area is called alpine distribution. It applies to species that are widespread in the alpine levels of individual high mountains in Eurasia, but never occur in the Arctic. An example of a purely oreotundral species is Boloria pales . It is a butterfly living in alpine tundras, which occurs from the Cantabrian Mountains to Taiwan for individual high mountains and still reaches the mountains of southern Siberia ( Altai , Sajan Mountains ) without penetrating the Arctic. Other examples of the alpine distribution in Europe are the Eros blue and numerous erebias such as Erebia oeme , Erebia albergana , Erebia pronoe , Erebia manto , Erebia sudetica , Erebia tyndarus , Erebia pharte , Erebia epiphron or Erebia gorge . Agriades glandon - Agriades pyrenaicus - Agriades dardanus are a vicarious clan pair of the arctic-alpine fauna and the oro-Mediterranean xeromontane mountains between the Artkis of the Alps, the Iberian and Balkan peninsulas and Asia Minor . While Agriades glandon is a polycentric Eurasian (circumpolar) tundro-alpine species and a representative of the alpine fauna, the other species formation took place in meridional refuges during the ice ages, which were most likely very close to today's highly fragmented locations and larval habitats offered to the Shaggy Man's Shield ( Androsace villosa ).

The Adamović line

The species that belong to the arctic-alpine area groups, in the so-called Adamović line, have a strict border to the south . This sharp dividing line is evident on the Balkan Peninsula. It is the dividing line between the Central European and Mediterranean vegetation zones. There are practically no arctic-alpine elements to the south of the Adamović line. De Lattin recognized this border postulated by Lujo Adamović in 1907 on the basis of plant-geographical features as a damming zone for Siberian fauna elements. The Hungarian entomologist Zoltán Varga further affirmed the Adamović line as the border between alpine and xeromontane butterfly area types. In addition to the climatic causes, substrate types , geomorphology and soil conditions and the resulting differences in vegetation are responsible for these faunistic differences. For the genetic lines of the south-east European high mountains with typical alpine zoning, an earlier genetic separation was found in arcto-alpine and alpine disjunctions. They belong to older genetic lines that survived the ice ages there and, in contrast to the alpines, are relics of the older ice age phases.

Phylogenetic evidence

The gray-brown Mohrenfalter - in Europe a high alpine butterfly that occurs from the Eastern Pyrenees to the tundras of the Arctic and Mongolia

The arctic-alpine species are phylogenetically well-studied groups. Both in the fauna ( Pardosa saltuaria , Graubrauner Mohrenfalter and Nebria rufescens ) as well as in the vegetation, the suspected connections of a continuous settlement in tundras between the ice centers of the Alps and the Nordic inland ice could be proven through phylogenetic relationships. Older lineages that are not based on post-glacial immigration were only found in the more southerly Balkan mountains.

Among the arctic-alpine plant species, Ranunculus glacialis , Arabis alpina and Veronica alpina were found to be colonized in the north-western Arctic from the Alps. In the case of Dryas octopetala , colonization took place from Northern Europe and Scandinavia via the main populations between the two glaciation centers. While in Minuartia biflora such as Carex atrofusca the populations in Northern Europe and the Alps had been separated for a long time. In Ranunculus pygmaeus , the closest related of the Alpine and Scandinavian populations were those of the Taymyr Peninsula in northern Siberia and the Urals.

Habitat types

Distribution of zonal and extrazonal tundras as a habitat for arctic-alpine, alpine and tundral species. The choice of color has been changed to make it easier to see on the original “Vegetation Zones” map.
  • Highly polar lichen u. Moostundra (10 - 80% plant cover )
  • Low polar dwarf shrub u. Meadow tundra (> 80% plant cover )
  • Subpolar mountain tundra
  • Mountain tundra of moderate latitudes as well as extrazonal alpine mats and the like. Heathens
  • Sub-polar meadows, heaths, etc. Moors

    • Arcto-alpine species are always tied to forest-free habitats . They often colonize rock and rubble sites or raised bogs , which are mostly characterized by periglacial process dynamics, i.e. constant alternation between periods of thaw and frost. The distribution of these tundra species was created by expansion during the cold ages with subsequent receding in the post-glacial warming. Originally, the arctic-alpine species inhabited large areas of the tundras in Central and Eastern Europe, which had become tree-free during the Ice Age. These areas between the glaciation centers in the Alps and Northern Europe had wide glacial valleys with periglacial frost debris zones in which the Ice Age animal species lived. After the inland glaciers melted and the alpine glaciers receded, the cold-loving species moved to higher latitudes and, in the south, to higher altitudes.

    Warm age micro-refuge of arctic-alpine species

    Stalkless catchfly ( Silene acaulis ) on periglacial debris at Vihren in Bulgaria

    Unlike the cold-age fauna, none of the arctic-alpine plant species was exterminated by the climatic oscillations in the Quaternary. However, some of the most heat-sensitive species have been displaced from regional flora in the interstadials. During the 1200 years of cold climatic relapse into full glacial conditions during the Younger Dryas period, u. a. Pedicularis hirsuta , Pecicularis lanata , Silene uralensis and Salix polaris no longer return to continental Europe or the British Isles. Interestingly enough, in Europe these species only colonize high-altitude locations in Scandinavia. Many arctic alpine species are now extinct in Great Britain and Ireland after the glacial maximum or the end of the Younger Dryas. In addition to the Pedicularis hirsuta , Pecicularis lanata , Silene uralensis and Salix polaris already mentioned , there are Coriospermum pallasii , Papaver Sect. Scapiflora , Ranunculus hyperboreus , Ranunculus aconitifolius , Silene uralensis and Stellaria crassifolia . In the British Isles Arenaria ciliata , Arenaria norvegica ssp. anglica , Aregaria norvegica ssp. norvegica , Astragalus alpinus , Koenigia islandica , Linnaea boralis , Lychnis alpina , Minuartia stricta , Minuartia rubella , Polemonium caerulaeum , Saxifraga cespitosa u. a.

    Not all of the species also migrated north in the interglacials to high latitudes or high steps in the mountains. Such locations, called microrefugia or "cryptic refugia", are also observed today in the post-glacial period. Microrefugia at low altitudes or low latitudes occur in Europe where the local conditions put more competitive, heat-loving (thermophilic) species at a disadvantage. In southern Europe, glacial relics are only to be found in the highest mountains and there often only in topographical regions. This particularly applies to the regions bordering the Mediterranean flora region. In Bulgaria, the Alpenspitzkiel in the almost 3000 m high Pirin is limited to periglacial debris layers or solifluction soils and flowing earths at altitudes of around 2600 m. Examples of extremely low-lying refuges in mountains that no longer rise high enough than an alpine step is formed on them can be found in sinkholes where cold air can collect. In various regions such as the Apennines or the Dinarides, these are retreats for the glacial flora. In the Orjen Mountains, the relict sites of Dryas octopetala closest to the Mediterranean can only be found within the boundary of a cold air lake at an altitude of only 1575 m. Here, too, the formation of periglacial niches is necessary for it to occur.

    Examples

    Stalkless catchfly ( Silene acaulis ) on Svalbard

    Well-known examples in the plant kingdom include silver arum ( Dryas octopetala ), herb willow ( Salix herbacea ), single-headed fleabane ( Erigeron uniflorus ), snow gentian ( Gentiana nivalis ), three-leaf rush ( Juncus trifidus ), nudibranch ( Kobresia myosuroides ), Alpine pointed keel ( Oxytropis campestris ), Alpine bluegrass ( Poa alpina ), nodular knotweed ( Bistorta vivipara ), stalkless cucumber ( Silene acaulis ) or two-flowered violet ( Viola biflora ). A total of 136 plant species can be classified as arcto-alpine elements in Europe. 131 occur in the Alps, 110 in the Carpathians, 92 in the Pyrenees, 77 on the Balkan Peninsula and 58 in the Apennines.

    In the animal kingdom there are arctic-alpine species in almost all groups. In particular, they have been well studied in butterflies . These include Pyrgus andromedae , Boloria napaea and Erebia pandrose . For many butterfly species with arcto-alpine disjunction, close connections between larval habitat, forage plants and biogeomorphological interactions can be assumed. The caterpillars of Pyrgus andromedae feed monophag on the silver arum. Therefore, due to the distribution of the forage plant, this butterfly species can hardly be found outside of periglacial debris locations.

    In birds that's Ptarmigan in the high mountains of the Pyrenees and Alps and circumpolar distribution disjoint. Similarly, but without a sub-area in the Pyrenees, the mountain hare is common in mammals . In addition to the circumpolar distribution, there is a glacial relic area in the Alps.

    The main centers of the arctic-alpine disjunction are the Alps, Carpathians, Pyrenees and the highest mountains on the Balkan Peninsula (excluding Mount Olympus ). On the Balkan Peninsula, since there are no continuous high mountains there, arctic-alpine elements occur only locally, especially in Montenegro ( Durmitor , Prokletije ), Kosovo (also Prokletije), in northern North Macedonia ( Šar Planina ) and in western Bulgaria ( Rila and Pirin ).

    literature

    • Vladimir Stevanović, Snežana Vukojičić, Jasmina Šinžar-Sekulić (2009): Distribution and diversity of Arctic-Alpine species in the Balkans . Plant Systematics and Evolution 283 (3/4): 219-235.

    Individual evidence

    1. ↑ Lexicon of Biology: arktoalpine Formen , Spektrum.de
    2. ↑ Akira S. Hirao, Mikio Watanabe, Shiro Tsuyuzaki, Ayako Shimono, Xuefeng Li, Takehiro Masuzawa, Naoya Wada 2017: Genetic diversity within populations of an arctic-alpine species declines with decreasing latitude across the Northern Hemisphere. Journal of Biogeography, vol. 44: 2740-2751. (Wiley Online Library: PDF)
    3. ↑ Schmitt, T .; Muster, C. & Schönswetter, P. 2010: Are Disjunct Alpine and Arctic-Alpine Animal and Plant Species in the Western Palearctic Really “Relics of a Cold Past”? In: Relict Species Phylogeography and Conservation Biology, 2010: 239-252
    4. ↑ a b Vladmir Stevanović, Snežana Vukojičić, Jasmina Šinžar-Sekulić, Maja Lazarević, Gordana Tomović, Kit Tan: Distribution and diversity of Arctic-Alpine species in the Balkans . Plant Systematics and Evolution, December 2009, 283.219, (PDF)
    5. ↑ a b c Hilary H. Birks 2008: Late-Quaternary history of arctic and alpine plants. Plant Ecology & Diversity. Vol. 1/2: November 2008: 135-146
    6. ↑ Thorsten Englisch 1999: Multivariate analyzes of the syn systematics and site ecology of the snow floor vegetation ( Arabidetalia caerulea ) in the Northern Limestone Alps. In: Stapfia. Volume 59, Linz 1999, pp. 30-31, ISSN 0252-192X, PDF on ZOBODAT
    7. ↑ Thorsten English 1999: p. 31
    8. ↑ Varga, Zoltan and Schmitt, Thomas 2008: Types of oreal and oreotundral disjunctions in the western Palearctic. Biological Journal of the Linnean Society, vol. 93: 415-430.
    9. ↑ Varga, Zoltan and Schmitt, Thomas 2008: pp. 422–423
    10. ↑ Yu-Feng Hsu 1997: Notes on Boloria pales yangi , ssp. nov., a remarkable disjunction in butterfly biogeography (Lepidoptera: Nymphalidae). Journal of Research on the Lepidoptera, vol. 34 / 1-4: 142-146 (researchgate: PDF)
    11. ↑ a b c Zoltan Varga (2014): Biogeography of the high mountain Lepidoptera in the Balkan Peninsula. Ekologija Montenegrina 1: 140-168. (PDF)
    12. ↑ Varga, Zoltán 1977: Zoogeographical classification of the Palearctic oreal fauna. In: Negotiations of the Sixth International Symposium on Entomofaunistics in Central Europe (Ed. Malicky, Hans), Springer Netherlands, 263-284.
    13. ↑ Schmitt, T .; Muster, C. & Schönswetter, P. 2010: Are Disjunct Alpine and Arctic-Alpine Animal and Plant Species in the Western Palearctic Really “Relics of a Cold Past”? In: Relict Species Phylogeography and Conservation Biology, 2010: 239-252
    14. ↑ Schmitt, T .; Muster, C. & Schönswetter, P. 2010: Are Disjunct Alpine and Arctic-Alpine Animal and Plant Species in the Western Palearctic Really “Relics of a Cold Past”? In: Relict Species Phylogeography and Conservation Biology, 2010: 239-252
    15. ↑ Entry arktisch-alpin in Lexikon der Biologie, Spektrum.de
    16. ↑ RMM Crawford 2008: Cold climate plants in a warmer world. Plant Ecology & Diversity, 1/2: November 2008: 285-297. (PDF)
    17. ^ Richard J. Abbott 2008: History, evolution and future of arctic and alpine flora: overview. Plant Ecology & Diversity. Vol. 1/2: November 2008: 129-133 (PDF)
    18. ↑ H. John. B. Birks and Katherine Willis 2008: Alpines, trees, and refugia in Europe. Plant Ecology & Diversity. Vol. 1/2: November 2008: 147-160
    19. ↑ RMM Crawford 2008: Cold climate plants in a warmer world. Plant Ecology & Diversity, 1/2: November 2008: 285-297. (PDF)
    20. ↑ Kozuharova, E., Richards, A., Hale, M., Benbassat, N. and Wolff, K. 2015: Another brick in the wall of the oxytropis campestris complex with an emphasis of three members of this group from Pirin Mts, the Balkans. In: Fabaceae (Ed. Wayne Garza), Nova Science Publishers, 61-108. ISBN 978-1-63482-200-8
    21. ↑ Pavle Cikovac & Ingo Hölzle 2018: Glacial relicts in the Mediterranean Dinarides - A phenomenon of cold-air poll microclimates ?. Botanica Serbica, vol. 42/1: 74. (Botanica Serbica: PDF)
    22. ^ Zoltan Varga (1996): Biogeography and evolution of boreal Lepidoptera in the Palaearctic. Acta Zoologica Academiae Scientiarum Hungaricae 42: 289-330.