Editing Selfish genetic element (section)

=== Greenbeards ===
A [[green-beard effect|greenbeard gene]] is a gene that has the ability to recognize copies of itself in other individuals and then make its carrier act preferentially toward such individuals. The name itself comes from thought-experiment first presented by William Hamilton<ref name=":27">{{cite journal | vauthors = Hamilton WD | title = The genetical evolution of social behaviour. I | journal = Journal of Theoretical Biology | volume = 7 | issue = 1 | pages = 1–16 | date = July 1964 | pmid = 5875341 | doi = 10.1016/0022-5193(64)90038-4| bibcode = 1964JThBi...7....1H | s2cid = 5310280 }}</ref> and then it was developed and given its current name by Richard Dawkins in ''The Selfish Gene.'' The point of the thought experiment was to highlight that from a gene's-eye view, it is not the genome-wide relatedness that matters (which is usually how kin selection operates, i.e. cooperative behavior is directed towards relatives), but the relatedness at the particular locus that underlies the social behavior.<ref name="TSG" /><ref name=":27" />

[[File:GreenbeardsAug18.png|thumb|The simplest form of greenbeard mechanism. An individual with the greenbeard allele preferentially helps a fellow greenbeard individual.]]

Following Dawkins, a greenbeard is usually defined as a gene, or set of closely linked genes, that has three effects:<ref>{{cite journal | vauthors = Gardner A, West SA | title = Greenbeards | journal = Evolution; International Journal of Organic Evolution | volume = 64 | issue = 1 | pages = 25–38 | date = January 2010 | pmid = 19780812 | doi = 10.1111/j.1558-5646.2009.00842.x | s2cid = 221733134 }}</ref>

# It gives carriers of the gene a phenotypic label, such as a greenbeard.
# The carrier is able to recognize other individuals with the same label.
# The carrier then behaves altruistically towards individuals with the same label.

Greenbeards were long thought to be a fun theoretical idea, with limited possibility of them actually existing in nature. However, since its conception, several examples have been identified, including in yeast,<ref>{{cite journal | vauthors = Smukalla S, Caldara M, Pochet N, Beauvais A, Guadagnini S, Yan C, Vinces MD, Jansen A, Prevost MC, Latgé JP, Fink GR, Foster KR, Verstrepen KJ | display-authors = 6 | title = FLO1 is a variable green beard gene that drives biofilm-like cooperation in budding yeast | journal = Cell | volume = 135 | issue = 4 | pages = 726–37 | date = November 2008 | pmid = 19013280 | pmc = 2703716 | doi = 10.1016/j.cell.2008.09.037 }}</ref> slime moulds,<ref>{{cite journal | vauthors = Queller DC, Ponte E, Bozzaro S, Strassmann JE | title = Single-gene greenbeard effects in the social amoeba Dictyostelium discoideum | journal = Science | volume = 299 | issue = 5603 | pages = 105–6 | date = January 2003 | pmid = 12511650 | doi = 10.1126/science.1077742 | bibcode = 2003Sci...299..105Q | s2cid = 30039249 }}</ref> and fire ants.<ref>{{cite journal | vauthors = Keller L, Ross KG | title = Selfish genes: a green beard in the red fire ant. | journal = Nature | year = 1998 | volume = 394 | issue = 6693 | pages = 573–575 | doi = 10.1038/29064 | bibcode = 1998Natur.394..573K | s2cid = 4310467 }}</ref> &nbsp;

There has been some debate whether greenbeard genes should be considered selfish genetic elements.<ref>{{cite journal | vauthors = Ridley M, Grafen A | title = Are green beard genes outlaws? | journal = Anim. Behav. | date = 1981 | volume = 29 | issue = 3 | pages = 954–955 | doi = 10.1016/S0003-3472(81)80034-6 | s2cid = 53167671 }}</ref><ref>{{cite journal | vauthors = Alexander RD, Bargia G | title = Group Selection, Altruism, and the Levels of Organization of Life. | journal = Annu Rev Ecol Syst | date = 1978 | volume = 9 | pages = 449–474 | doi = 10.1146/annurev.es.09.110178.002313 }}</ref><ref name=":23">{{cite journal | vauthors = Biernaskie JM, West SA, Gardner A | title = Are greenbeards intragenomic outlaws? | journal = Evolution; International Journal of Organic Evolution | volume = 65 | issue = 10 | pages = 2729–42 | date = October 2011 | pmid = 21967416 | doi = 10.1111/j.1558-5646.2011.01355.x | s2cid = 6958192 }}</ref> Conflict between a greenbeard locus and the rest of the genome can arise because during a given social interaction between two individuals, the relatedness at the greenbeard locus can be higher than at other loci in the genome. As a consequence, it may in the interest of the greenbeard locus to perform a costly social act, but not in the interest of the rest of the genome.<ref name=":23" />

In conjunction with selfish genetic elements, greenbeard selection has also been used as a theoretical explanation for suicide.<ref>{{Cite journal|last=Wiley|first=James C.|date=2020-12-01|title=Psychological Aposematism: An Evolutionary Analysis of Suicide|journal=Biological Theory|language=en|volume=15|issue=4|pages=226–238|doi=10.1007/s13752-020-00353-8|s2cid=219734814|issn=1555-5550|doi-access=free}}</ref>