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{{technical|date=January 2012}}

'''Genic capture''' is a hypothesis explaining the maintenance of [[genetic variance]] in traits under [[sexual selection]]. A classic problem in sexual selection is the fixation of [[alleles]] that are beneficial under strong selection, thereby eliminating the benefits of [[mate choice]]. Genic capture resolves this [[lek paradox|paradox]] by suggesting that [[Quantitative genetics|additive genetic variance]] of [[Sexual selection|sexually selected traits]] reflects the genetic variance in total condition.<ref name="rowehoule">{{cite journal|last=Rowe|first=Locke|coauthors=Houle, David|title=The capture of genetic variance by condition dependent traits|journal=[[Proceedings of the Royal Society B]]|year=1996|volume=263|pages=1415–1421|doi=10.1098/rspb.1996.0207|issue=1375}}</ref> A deleterious [[mutation]] anywhere in the [[genome]] will adversely affect condition, and thereby adversely affect a condition-dependent sexually selected trait. Genic capture therefore resolves the [[lek paradox]] by proposing that recurrent deleterious mutation maintains additive genetic variance in fitness by incorporating the entire [[mutation load]] of an individual. Thus any condition-dependent trait "captures" the overall genetic variance in condition. Rowe and Houle argued that genic capture ensures that [[Handicap principle|good genes]] will become a central feature of the evolution of any sexually selected trait.

== Condition ==

The key quantity for genic capture is vaguely defined as "condition." The hypothesis only defines condition as a quantity that correlates tightly with overall [[fitness (biology)|fitness]], such that [[directional selection]] will always increase average condition over time. Condition should, in general, reflect overall energy acquisition, such that life-history variation reflects differential allocation to survival and sexual signalling. Genetic variation in condition should be very broadly affected by any changes in the genome. Close to [[genetic equilibrium|equilibrium]] any mutation should be [[Fisher's geometric model|deleterious]], thereby leading to non-zero overall mutation rate, maintaining variance in fitness.

== Rowe and Houle's Quantitative Genetic Model ==
Rowe and Houle's simple model defines a trait as the result of three heritable components, a condition-independent component <math>a</math>, epistatic modification <math>b</math> and condition, suggesting the following function for a trait:

<math>
T = a + bC
</math>

where <math>C</math> is the condition of an individual.  Loci contributing to <math>C</math> are loosely linked and independent of loci contributing to <math>a</math> and <math>b</math>.  Rowe and Houle then find the expected variance of <math>T</math> and ignored higher-order terms (i.e. products of variances):

<math>
G_T \approx G_a + \bar{b}^2 G_C + \bar{C}^2 G_b
</math>

where <math>G_T</math> represents the [[genetic variance]] in the signal and analogously for other traits.  Under [[directional selection]] on <math>T</math>, the loci underlying <math>a</math> and <math>b</math> may lose all genetic variance.  However, there is no qualitative difference in directional selection on <math>C</math> between [[stabilizing selection]] (i.e. no sexual selection) and directional selection on <math>T</math>.  Therefore the second term <math>\bar{b}^2 G_C</math> will remain positive (due to biased mutation) and dominate <math>G_T</math> under sexual selection.

== Other Applications ==
Genic capture can also play a role in accelerating adaptation to new environments.<ref name="lorch">{{cite journal|last=Lorch|first=Patrick|title=Condition-dependent sexual selection can accelerate adaptation|journal=Evolutionary Ecology Research|year=2003|volume=5|pages=867–881|coauthors=Stephen Proulx, Locke Rowe, Troy Day}}</ref>

== Comparisons ==

Genic capture was proposed as a simpler alternative to another theory explaining the lek paradox<ref name="moller">{{cite journal|last=Pomiankowski|first=Andrew|coauthors=Moller, A.P.|journal=[[Proceedings of the Royal Society B]] | year=1995|volume=260|pages=21–29|doi=10.1098/rspb.1995.0054|title=A Resolution of the Lek Paradox|issue=1357}}</ref> that proposed that sexual selection creates [[disruptive selection]], i.e. positive selection for genetic variance.  Genic capture does not require any particular fitness function.

== References ==
{{Reflist}}

<!--- Categories --->

[[Category:Evolutionary biology]]
[[Category:Sexual selection]]