Refugium (population biology)

European LGM refugia, 20 kya.

In biology, a refugium (plural: refugia) is a location which supports an isolated or relict population of a once more widespread species. This isolation (allopatry) can be due to climatic changes, geography, or human activities such as deforestation and overhunting.

Present examples of refuge species are the mountain gorilla, isolated to specific mountains in central Africa, and the Australian sea lion, isolated to specific breeding beaches along the south-west coast of Australia, due to humans taking so many of their number as game. This resulting isolation, in many cases, can be seen as only a temporary state; however, some refugia may be longstanding, thereby having many endemic species, not found elsewhere, which survive as relict populations. The Indo-Pacific Warm Pool has been proposed to be a longstanding refugium, based on the discovery of the "living fossil" of a marine dinoflagellate called Dapsilidinium pastielsii, currently found in the Indo-Pacific Warm Pool only.[1]

In anthropology, refugia often refers specifically to Last Glacial Maximum refugia, where some ancestral human populations may have been forced back to glacial refugia, similar small isolated pockets in the face of the continental ice sheets during the last glacial period. Going from west to east, suggested examples include the Franco-Cantabrian region (in northern Iberia), the Italian and Balkan peninsulas, the Ukrainian LGM refuge, and the Bering Land Bridge. Archaeological and genetic data suggest that the source populations of Paleolithic humans survived the glacial maxima (incl. the Last Glacial Maximum) in sparsely wooded areas and dispersed through areas of high primary productivity while avoiding dense forest cover.[2]

Speciation

As an example of a locale refugia study, Jürgen Haffer first proposed the concept of refugia to explain the biological diversity of bird populations in the Amazonian river basin. Haffer suggested that climatic change in the late Pleistocene led to reduced reservoirs of habitable forests in which populations become allopatric. Over time, that led to speciation: populations of the same species that found themselves in different refugia evolved differently, creating parapatric sister-species. As the Pleistocene ended, the arid conditions gave way to the present humid rainforest environment, reconnecting the refugia.

Scholars have since expanded the idea of this mode of speciation and used it to explain population patterns in other areas of the world, such as Africa, Eurasia, and North America. Theoretically, current biogeographical patterns can be used to infer past refugia: if several unrelated species follow concurrent range patterns, the area may have been a refugium. Moreover, the current distribution of species with narrow ecological requirements tend to be associated with the spatial position of glacial refugia.[3]

Simple environment examples of temperature

One can provide a simple explanation of refugia involving core temperatures and exposure to sunlight. In the northern hemisphere, north-facing sites on hills or mountains, and places at higher elevations count as cold sites. The reverse are sun- or heat-exposed, lower-elevation, south-facing sites: hot sites. (The opposite directions apply in the southern hemisphere.) Each site becomes a refugium, one as a "cold-surviving refugium" and the other as a "hot-surviving refugium". Canyons with deep hidden areas (the opposite of hillsides, mountains, mesas, etc. or other exposed areas) lead to these separate types of refugia.

A concept not often referenced is that of "sweepstakes colonization":[4][5] when a dramatic ecological event occurs, for example a bolide strike, and global, multiyear effects occur. The sweepstake-winning species happens to already be living in a fortunate site, and their environment is rendered even more advantageous, as opposed to the "losing" species, which immediately fails to reproduce.[4][5]

See also

Notes

  1. ↑ Mertens, K.N.; Takano, Y.; Head, M.J.; Matsuoka, K. (2014). "Living fossils in the Indo-Pacific warm pool: A refuge for thermophilic dinoflagellates during glaciations". Geology. 42: 531–534. doi:10.1130/G35456.1.
  2. ↑ Gavashelishvili, A.; Tarkhnishvili, D. (2016). "Biomes and human distribution during the last ice age". Global Ecology and Biogeography. 25: 563–574. doi:10.1111/geb.12437.
  3. ↑ Tarkhnishvili D, Gavashelishvili A, Mumladze L. 2012. Palaeoclimatic models help to understand current distribution of Caucasian forest species. Biol. J. Linn. Soc. 105:231-248
  4. 1 2 Petit, Rémy J; Hu, Feng Sheng; Dick, Christopher W. (2008). "Forests of the Past: A Window to Future Changes". Science. 320 (5882): 1450–1452. doi:10.1126/science.1155457.
  5. 1 2 Penny, Norman D; Penny, Fabio R. (10 April 2001). "Gulf of Guinea Islands Biodiversity Project". California Academy of Sciences. Retrieved 26 April 2016.
  6. ↑ "Unepscs.org". Refugia.unepscs.org. Retrieved 2012-03-12.

References

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