Refugial space

from Wikipedia, the free encyclopedia
Nunatakker - ice-free "islands" in the eternal ice - are geographically and climatically the most extreme refuges for some life forms

Refugial areas (from the Latin refugium = place of refuge, English : refugia ; also conservation areas ) are generally habitats to which animal or plant species retreat because, for various reasons, survival is no longer possible in their original (mostly much larger) habitats. These can either be ecoregions that have become significantly smaller due to climatic , anthropogenic or other massive influences or that have emerged in a similar composition due to the changed conditions in other climatic zones (and have displaced the ecosystems that were previously typical there).

The term was introduced into ecology as a technical term in 1955 by the pollen scientist Calvin J. Heusser when he described the shrunken and shifted distribution areas of plant species in Canada during the last Ice Age glaciation .

In a narrower sense the term (mostly as will Ice Age , glacial or Pleistocene refuge → section Air refuge ) still to areas used in which a certain kind during a full glacial / interglacial cycle has survived. This theory was initially only valid for areas of the northern hemisphere , but was later applied to other climatic zones and ecoregions, for example in 1961 by James Allen Keast on the bird life of Australia, in 1969 by Jürgen Haffer on the tropical rainforests in the Amazon basin , and in 1966 by Reginald Ernest Moreau on the bird world of Africa and in 1975 by Harry Godwin on the flora of the British Isles.

In a broader sense, the term is now also applied to individual animals and plants that are "relatively safe" from harmful and energy-consuming environmental influences in a (current) refuge:

Example of running water : Self-cleaning and the associated self-regulation lead to a restoration of the initial state of the running water after a heavy load ( flood , a lot of wastewater ). Then the animals emerge from the refuges and repopulate the area, so that the ecosystem with the abiotic and biotic factors is restored. Typical refuge areas in running waters are, for example, the hyporheic interstitial and flow-calmed bank areas.

Climate refuge

Locations of tropical rainforests and temperate deciduous tree species as an example of so-called “short-term” and “long-term” refuges during the last ice age maximum

As a result of global climate changes (e.g. during the Ice Ages), refuges for numerous species have repeatedly emerged. A distinction is made between two different types (especially in English-language literature):

Short-term refugia

“Short-term refuges” are those areas of refuge that are characterized by the temporary, extensive conversion of ecosystems through the immigration of new species . They occur mainly in the (today's) temperate zone . Local climates prevailed in such retreat areas during the ice ages, for example , which ensured the survival of plant and animal species and thus enabled the post-glacial return to their original habitats. In contrast to the long-term refuges , the original habitats were completely lost here at times.

In the biogeography of the mountains, a distinction is also made between Nunatakker (partly ice-free, isolated mountain peaks within a glacier ), peripheral refuges (areas in the immediate vicinity of the glacier) and lowland refuges (areas adjacent to the glacier region, also called periglacial refuges ).

Long-term (stable) refugia

“Long-term (stable) refuges” emerged during the cold ages, mainly in the tropics, as a result of a drastic reduction in size and fragmentation of large-scale ecosystems ( forests and savannas ) into many smaller “island habitats”. The habitat of the species that live there is shrinking, but without disappearing entirely, as is the case with the short-term refuges . The areas that were "island refuges" in the last Ice Age are therefore among the oldest ecosystems on earth.

The transfer of the refugee theory to tropical areas in the 1960s and 70s enjoyed great popularity for a long time, as it was believed that the existence of these long-term refuges explained the enormous biodiversity of some rainforests .

It is certain that the development history of the tropical rainforests of Madagascar, Australia and New Caledonia in the refuges goes back uninterruptedly to the end of the Cretaceous Period ( Campanium ) and in South America and Africa at least to the middle Eocene ( Bartonian ).

However, the hypothesis of forest refuges has changed over time: It was found that the refuges were smaller, more widely scattered, adjacent to more different other types of vegetation and, above all, less homogeneously occupied than originally assumed, since the tropical climate was colder during the ice ages, was drier and more seasonal than today.

In the last few decades, studies have been carried out that confirm and refute almost every aspect of the forest refuge hypothesis . The biggest point of contention is based primarily on the still inadequate reconstruction of the dimensions of tropical forest and savannah areas in the cold ages. There is only agreement on the fact that the enormous diversity cannot be explained by this one mechanism, but by a whole series of factors whose effects and proportions are still largely unexplained ( e.g. mountain formation , changes in river courses and water levels or the domestication of species by humans).

Ice Age relics

Today's refuges for some creatures of the Ice Age mammoth steppe are in the polar tundras and cold deserts of Europe, Asia and North America. The species composition of the tundra does not correspond to that of the mammoth steppes (which were more like today's highland steppes of Tibet ), so that the phenomena of refuge and glacial relic meet here.

homo sapiens

Refugia areas during the cold maximum of the last Ice Age (glacial refugia) were found for humans especially in the Franco-Cantabrian region , for many animals and plants of the temperate zone on the Mediterranean (52 regions were identified), but also relatively northern refuges were occupied , so the wooded region of the Carpathians in the border area to permafrost .

Refugial spaces for subspecies

Since glacial refuges housed numerous species, it was assumed that this also applied to various subspecies . It was assumed that such a high level of biodiversity arose in a small space. However, studies could not support this assumption.

Rather, the presence of several subspecies of a species indicates their genetic differentiation through the separation of their habitats into different refuge areas. Their populations are usually small and therefore relatively homogeneous genetic compositions develop there within limited periods of time, so that no subspecies can arise. If the separation times last long enough, the species in each refuge develop separately into new species ( allopatric speciation ) .

The discovery and description of refuges and the assignment of the resulting subspecies makes it possible to better reconstruct the underlying paleoclimatic course chronologically.

See also

Individual evidence

  1. ↑ Calvin J. Heusser: Pollen Profiles from the Queen Charlotte Islands, British Columbia. In: Canadian Journal of Botany. Volume 33, No. 5, 1955, pp. 429-449, doi: 10.1139 / b55-036
  2. ↑ Godfrey M. Hewitt: Some genetic consequences of ice ages, and their role in divergence and speciation. In: Biological Journal of the Linnean Society. Volume 58, No. 3, 1996, pp. 247-276, DOI: 10.1111 / j.1095-8312.1996.tb01434.x
  3. ^ A b Daniel Gomes da Rocha, Igor L. Käfer: What has become of the refugia hypothesis to explain biological diversity in Amazonia? in "Ecology and Evolution", March 27, 2019, online , paragraphs 2 and 4.
  4. ↑ Glossary of teaching materials on the subject A stream is more than water ... , p. 247, ed. from the Hessian Ministry of the Environment (PDF; 279 kB), dump dated November 26, 2015
  5. ↑ EG Kauffman u. PJ Harries (authors), MB Hart (eds.): Biotic Recovery from Mass Extinction Events. Geological Society Special Publication No. 102, Geological Society of London, 1996, ISBN 1-897799-45-4 , pp. 22-23.
  6. ↑ Holderegger, R., Thiel-Egenter, C. (2009): A discussion of different types of glacial refugia used in mountain biogeography and phytogeography. Journal of Biogeography 36, 476-480. pdf version
  7. ↑ Jörg S. Pfadenhauer, Frank A. Klötzli: Vegetation of the earth: Fundamentals, ecology, distribution. Springer Spectrum, Berlin / Heidelberg 2014, ISBN 978-3-642-41949-2 . P. 87.
  8. ↑ Manfred Eggert : The 'primeval forest' as a living space and projection space: The inner Central Africa * , in Svend Hansen, Michael Meyer (Ed.): Parallele Raumkonzepte , Walter de Gruyter, Berlin / Boston 2013, ISBN 978-3-11-029094 -3 . Pp. 43-44.
  9. Jump up ↑ P. Schönswetter, I. Stehlik, R. Holderegger, A. Tribsch: Molecular evidence for glacial refugia of mountain plants in the European Alps. In: Molecular Ecology. Volume 14, No. 11, 2005, pp. 3547-3555, doi : 10.1111 / j.1365-294X.2005.02683.x .
  10. ↑ A. Achili et al .: The molecular dissection of mtDNA haplogroup H confirms that the Franco-Cantabrian glacial refuge was a major source for the European gene pool . In: The American Journal of Human Genetics. Volume 75, No. 5, 2004, pp. 910-918, doi : 10.1086 / 425590 (full text).
  11. ↑ Frederic Medail, Katia Diadema: Glacial refugia influence plant diversity patterns in the Mediterranean Basin. In: Journal of Biogeography. Volume 36, No. 7, 2009, pp. 1333-1345, doi : 10.1111 / j.1365-2699.2008.02051.x .
  12. ↑ Petr Kotlík et al .: A northern glacial refugium for bank voles (Clethrionomys glareolus). In: PNAS . Volume 103, No. 40, 2006, pp. 14860-14864, doi : 10.1073 / pnas.0603237103 .
  13. ↑ Rémy J. Petit et al .: Glacial refugia: hotspots but not melting pots of genetic diversity. In: Science . Volume 300, No. 5625, 2003, pp. 1563-1565, doi : 10.1126 / science.1083264 .
  14. ↑ Alex Widmer, Christian Lexer: Glacial refugia: sanctuaries for allelic richness, but not for gene diversity. In: Trends in Ecology & Evolution. Volume 16, No. 6, 2001, pp. 267-269, doi : 10.1016 / S0169-5347 (01) 02163-2 .
  15. ↑ K. Holder, R. Montgomerie, VL Friesen: A test of the glacial refuguim hypothesis using patterns of mitochondrial and nuclear DNA sequences variation in rock ptarmigan (Lagopus mutus). In: evolution. 53, No. 6, December 1999, pp. 1936-1950, doi : 10.2307 / 2640452 .
  16. ↑ Andrea Grill et al .: Molecular phylogeography of European Sciurus vulgaris: refuge within refugia? In: Molecular Ecology. Volume 18, No. 12, 2009, pp. 2687-2699, doi : 10.1111 / j.1365-294X.2009.04215.x .
  17. ↑ SA Byun, BF Koop, TE Reimchen: North American black bear mtDNA phylogeography: implications for morphology and the Haida Gwaii glacial refugium controversy. In: evolution. Volume 51, No. 5, October 1997, pp. 1647-1653, full text (PDF) .