A glacial refugium (plural glacial refugia) is a geographic region which made possible the survival of flora and fauna during ice ages and allowed for post-glacial re-colonization.[1][2] Different types of glacial refugia can be distinguished, namely nunatak, peripheral, and lowland.[3] Glacial refugia have been suggested as a major cause of floral and faunal distribution patterns in both temperate and tropical latitudes.[4][5][6] With respect to disjunct populations of modern-day species, especially in birds,[7][8] doubt has been cast on the validity of such inferences, as much of the differentiation between populations observed today may have occurred before or after their restriction to refugia.[9][10] In contrast, isolated geographic locales that host one or more critically endangered species (regarded as paleoendemics or glacial relicts) are generally uncontested as bona fide glacial refugia.[11]

Identification

Traditionally, the identification of glacial refugia has occurred through palaeoecological analysis, which examines fossil organisms and their remains to determine the origins of modern taxa.[5] For example, paleoecological approaches have been used to reconstruct the distributions of pollen in Europe for the 13,000 years since the last glaciation. Researchers in this case ultimately established the spread of forest trees from the mountainous southern fringe of Europe, which suggests that this area served as a glacial refugium during this time.[12]

Types

In studies exploring the extent of glacial refugia in mountain species, three distinct types of glacial refugium have been identified.[3]

Nunatak

A nunatak is a type of glacial refugium that is located on the snow-free, exposed peaks of mountains, which lie above the ice sheet during glaciations.[3] The identification of ‘diversity hotspots’ in areas, which should have been migration regions during major glacial episodes, is evidence for nunatak glacial refugia.[13] For example, the Monte Rosa mountain ranges, the Avers, and the Engadine and the Bernina are all floristically rich proposed nunatak regions, which are indicative nunatak glacial survival.[13]

Peripheral

Like nunataks, peripheral glacial refugia exist within mountain systems; they differ in that they are located at the borders of mountain systems.[3] Evidence for peripheral refugia can be found along the borders of the Carpathian Mountains, Pyrenees, and European Alps, all of which were once glaciated mountain systems. For example, using the amplified fragment length polymorphism (AFLP) technique, researchers have inferred survival of Phyteuma globulariifolium in peripheral refugia in the European Alps.[14]

Lowland

Lowland glacial refugia, unlike nunatak and peripheral glacial refugia, are found at low elevations rather than in mountains.[3] Situated beyond the limits of ice shields, lowland refugia have been identified for a number of plant and animal species. In Europe, for example, researchers using allozyme analysis have been able to confirm the continuous distribution of Zygaena exulans in between the foothills of the Pyrenees and the Alps during the last ice age.[15]

In eastern North America, lowland glacial refugia along the Atlantic and Gulf Coasts host endemic plants — some of which are rare, even endangered, and others entail the most southerly disjunct populations of plants that commonly appear only hundreds of miles to the north. Major rivers draining southward from the Appalachian Mountains are associated with a gradation of paleoendemic tree species. These range from the extinct Critchfield spruce near the outlet of the Mississippi River, to extinct-in-the-wild Franklinia along the Altamaha River, to the critically endangered Florida torreya and Florida yew at the downstream end of the Chattahoochee River system.[11][16] (See illustration at right.)

See also

References

  1. ^ Horsák, Michal; Limondin-Lozouet, Nicole; Juřičková, Lucie; Granai, Salomé; Horáčková, Jitka; Legentil, Claude; Ložek, Vojen (15 June 2019). "Holocene succession patterns of land snails across temperate Europe: East to west variation related to glacial refugia, climate and human impact". Palaeogeography, Palaeoclimatology, Palaeoecology. 524: 13–24. doi:10.1016/j.palaeo.2019.03.028. S2CID 134640979. Retrieved 14 November 2022.
  2. ^ The encyclopedia of earth, http://www.eoearth.org/view/article/155685/
  3. ^ a b c d e 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.
  4. ^ Petit, Rémy J.; Aguinagalde, Itziar; Beaulieu, Jacques-Louis de; Bittkau, Christiane; Brewer, Simon; Cheddadi, Rachid; Ennos, Richard; Fineschi, Silvia; Grivet, Delphine (2003-06-06). "Glacial Refugia: Hotspots But Not Melting Pots of Genetic Diversity". Science. 300 (5625): 1563–1565. Bibcode:2003Sci...300.1563P. doi:10.1126/science.1083264. ISSN 0036-8075. PMID 12791991. S2CID 34876930.
  5. ^ a b PROVAN, J; BENNETT, K (2008-10-01). "Phylogeographic insights into cryptic glacial refugia". Trends in Ecology & Evolution. 23 (10): 564–571. doi:10.1016/j.tree.2008.06.010. ISSN 0169-5347. PMID 18722689.
  6. ^ Rull, Valentí (2011-10-01). "Neotropical biodiversity: timing and potential drivers". Trends in Ecology & Evolution. 26 (10): 508–513. doi:10.1016/j.tree.2011.05.011. ISSN 0169-5347. PMID 21703715.
  7. ^ Brumfield, Robb T. (2012-07-01). "Inferring the Origins of Lowland Neotropical Birds". The Auk. 129 (3): 367–376. doi:10.1525/auk.2012.129.3.367. ISSN 0004-8038. S2CID 83697136.
  8. ^ Bermingham, E.; Rohwer, S.; Freeman, S.; Wood, C. (1992-07-15). "Vicariance biogeography in the Pleistocene and speciation in North American wood warblers: a test of Mengel's model". Proceedings of the National Academy of Sciences. 89 (14): 6624–6628. Bibcode:1992PNAS...89.6624B. doi:10.1073/pnas.89.14.6624. ISSN 0027-8424. PMC 49554. PMID 11607307.
  9. ^ Klicka, John; Zink, Robert M. (1997-09-12). "The Importance of Recent Ice Ages in Speciation: A Failed Paradigm". Science. 277 (5332): 1666–1669. doi:10.1126/science.277.5332.1666. ISSN 0036-8075.
  10. ^ Colinvaux, P. A.; De Oliveira, P. E.; Bush, M. B. (2000-01-01). "Amazonian and neotropical plant communities on glacial time-scales: The failure of the aridity and refuge hypotheses". Quaternary Science Reviews. 19 (1–5): 141–169. Bibcode:2000QSRv...19..141C. doi:10.1016/S0277-3791(99)00059-1.
  11. ^ a b Delcourt, Hazel R; Delcourt, Paul A (October 1975). "The Blufflands: Pleistocene Pathways into the Tunica Hills". American Midland Naturalist. 94 (2): 385–400. doi:10.2307/2424434. JSTOR 2424434.
  12. ^ Munaut, André-V. (May 1986). "An Atlas of past and present pollen maps of Europe: 0–13,000 years ago". Review of Palaeobotany and Palynology. 47 (3–4): 411–412. doi:10.1016/0034-6667(86)90044-8. ISSN 0034-6667.
  13. ^ a b Stehlik, Ivana (2000-06-01). Nunataks and peripheral refugia for alpine plants during quaternary glaciation in the middle part of the Alps. Birkhäuser. OCLC 753524599.
  14. ^ Schönswetter, P.; Tribsch, A.; Barfuss, M.; Niklfeld, H. (December 2002). "Several Pleistocene refugia detected in the high alpine plant Phyteuma globulariifolium Sternb. & Hoppe (Campanulaceae) in the European Alps". Molecular Ecology. 11 (12): 2637–2647. doi:10.1046/j.1365-294x.2002.01651.x. ISSN 0962-1083. PMID 12453246. S2CID 14302480.
  15. ^ Schmitt, Thomas; Hewitt, Godfrey M. (2004-05-07). "Molecular biogeography of the arctic-alpine disjunct burnet moth species Zygaena exulans (Zygaenidae, Lepidoptera) in the Pyrenees and Alps". Journal of Biogeography. 31 (6): 885–893. doi:10.1111/j.1365-2699.2004.01079.x. ISSN 0305-0270. S2CID 86301042.
  16. ^ Barlow, Connie. "Paleoecology and the Assisted Migration Debate: Why a Deep-Time Perspective Is Vital (Torreya taxifolia as exemplar)". Torreya Guardians. Retrieved 23 June 2022.
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