- Gloger's rule
Gloger's Rule is a zoological rule which states that within a
species ofendotherms , more heavily pigmented forms tend to be found in morehumid environments, e.g. near theequator . It was named after thezoologist Constantin Wilhelm Lambert Gloger , who first remarked upon this phenomenon in1833 in a review ofcovariation of climate and avian plumage color. [Gloger (1833)] Gloger found out that birds in more humid habitat tended to be darker than their relatives from regions with higheraridity . Over 90% of the species researched conform to this rule.Fact|date=February 2007An explanation of Gloger's rule in the case of birds appears to be the increased resilience of dark feathers to feather (and hair-degrading) bacteria (such as "
Bacillus licheniformis "). Feathers in humid environments have a greater bacterial load and humid environments are more suitable for microbial growth, but dark feathers or hair are more difficult to break down. [Burtt & Ichida (2004)] More resilienteumelanin s - dark brown to black - are deposited in hot and humid regions, whereas inarid regions,pheomelanin s - reddish to sandy color - predominate due to the benefit ofcrypsis .Among
mammal s, there is a marked tendency in equatorial and tropical regions to have a darker skin color than poleward relatives. In this case, the underlying cause is probably the need to better utilize the sun'sUV radiation with decreasinglatitude . Absorption of a certain amount of UV radiation is necessary for the production of certainvitamin s, notablyVitamin D ("see also"Osteomalacia ).This principle is also vividly demonstrated amongst human populations. [Ember "et al." (2002)] Populations that evolved in sunnier environments closer to the equator tend to be darker pigmented than populations originating farther from the equator. There are exceptions, however; among the most well-known are the Tibetans and
Inuit , who have darker skin than might be expected from the latitude at which they evolved. In the first case, this is apparently an adaptation to the extremely high UV irradiation on theTibetan Plateau , whereas in the second case, the necessity to absorb UV radiation is alleviated by a diet that is naturally rich inVitamin D .ee also
*
Allen's rule
*Bergmann's Rule Footnotes
References
* (2004): Gloger's Rule, feather-degrading bacteria, and color variation among Song Sparrows. "Condor" 106(3): 681-686. doi|10.1650/7383 [http://www.public.asu.edu/~kjmcgraw/pubs/Condor04b.pdf PDF fulltext]
* (2002): "Anthropology" (10th ed.). Prentice Hall.
* (1833): "Das Abändern der Vögel durch Einfluss des Klimas". August Schulz, Breslau. de icon
Wikimedia Foundation. 2010.