Green-beard effect: Difference between revisions
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The [[selfish gene theory]] postulates that [[natural selection]] will increase the frequency of those genes whose [[Phenotype|phenotypic]] effects ensure their successful [[DNA replication|replication]]. A [[gene]] for [[altruism]] can be favored by selection if the altruism is primarily directed at other individuals who share the same gene ([[kin selection]]). |
'''Green-beard effect''' is term coined to help explain behavior such as [[altruism]]. The notion of "green beard" is simply an example of an easily-recognizable (if not likely) trait. The [[selfish gene theory]] postulates that [[natural selection]] will increase the frequency of those genes whose [[Phenotype|phenotypic]] effects ensure their successful [[DNA replication|replication]]. A [[gene]] for [[altruism]] can be favored by selection if the altruism is primarily directed at other individuals who share the same gene ([[kin selection]]). |
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A '''green-beard effect''' gene (or linked genes) produces three phenotypic effects: |
A '''green-beard effect''' gene (or linked genes) produces three phenotypic effects: |
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Revision as of 17:20, 14 October 2009
Green-beard effect is term coined to help explain behavior such as altruism. The notion of "green beard" is simply an example of an easily-recognizable (if not likely) trait. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. A gene for altruism can be favored by selection if the altruism is primarily directed at other individuals who share the same gene (kin selection).
A green-beard effect gene (or linked genes) produces three phenotypic effects:
- a perceptible trait — the hypothetical green beard;
- recognition of this trait in others; and
- preferential treatment to those recognized.
So, this gene is directly recognizing copies of itself, regardless of average relatedness.
Green-beard altruism could, strictly speaking, increase the presence of green-beard phenotypes in a population even if genes are assisting other genes that are not exact copies of themselves in a molecular sense: all that is required is that they produce the three phenotypic characteristics described above. Green beard genes are vulnerable to mutant genes arising that produce the perceptible trait without the helping behaviour.
The idea of a green-beard gene was proposed by William D. Hamilton in his landmark articles of 1964 [1][2], and named as "Green Beard" gene by Richard Dawkins in his classic book The Selfish Gene of 1976. [3]
Examples
The concept remained a theoretical possibility under Dawkins' selfish gene model until 1998, when a green-beard gene was first found in nature, in the red imported fire ant (Solenopsis invicta). Workers selectively kill egg-laying queens homozygous for one specific allele of the locus Gp-9.[4]
The gene csaA in Dictyostelium discoideum, discovered in 2003, codes for an adhesin essential for multicellular fruiting body formation on soil.[5]
In 2006, green beard-like recognition was seen in the cooperative behavior among color morphs in side-blotched lizards, although the traits appear to be encoded by multiple loci across the genome.[6]
A more recent example, found in 2008, is a gene that makes brewer's yeast clump together in response to a toxin such as alcohol.[7]
References
- ^ Hamilton WD (1964). "The genetical evolution of social behaviour. I.". J Theor Biol. 7 (1): 1–16. PMID 5875341.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Hamilton WD (1964). "The genetical evolution of social behaviour. II". J Theor Biol. 7 (1): 17–52. PMID 5875340.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Dawkins, Richard. The Selfish Gene. Oxford University Press, Oxford.
{{cite book}}: Cite has empty unknown parameter:|month=(help); Text "ISBN 0-19-217773-7" ignored (help) - ^ Keller & Ross. "Selfish genes: a green beard in the red fire ant", Nature 394: 573-575, August 6, 1998.
- ^ Queller DC, Ponte E, Bozzaro S, Strassmann JE (2003). "Single-gene greenbeard effects in the social amoeba Dictyostelium discoideum" (PDF). Science. 299 (5603): 105–106. PMID 12511650.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Sinervo B, Chaine A, Clobert J, Calsbeek R, Hazard L, Lancaster L, McAdam AG, Alonzo S, Corrigan G, Hochberg ME (2006). "Self-recognition, color signals, and cycles of greenbeard mutualism and altruism". Proc Natl Acad Sci U S A. 103 (19): 7372–7377. PMID 16651531.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ http://www.seedmagazine.com/news/2008/12/yeast_gone_wild.php
Others:
- Haig, D. (1997) The social gene. In Krebs, J. R. & Davies, N. B. (editors) Behavioural Ecology: an Evolutionary Approach, 4th ed. pp. 284-304. Blackwell Publishers, London.
- Green Beard Ethnic Nepotism? on-line discussion about the topic by various authors, December 22, 2004, accessed Jan 2008
- Grafen, Alan Green beard as death warrant 1998, Nature, accessed Jan 2008 - short discussion and critique on the possible existence of a green beard gene