Genic capture

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 ${\displaystyle a}$, epistatic modification ${\displaystyle b}$ and condition, suggesting the following function for a trait:

${\displaystyle T=a+bC}$

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

${\displaystyle G_T\approx G_a+{\overline{b}}^2{G}_C+{\overline{C}}^2{G}_b}$

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

Other applications

Genic capture can also play a role in accelerating adaptation to new environments.

Comparisons

Genic capture was proposed as a simpler alternative to another theory explaining the lek paradox that proposed that sexual selection creates disruptive selection, i.e. positive selection for genetic variance. Genic capture does not require any particular fitness function.