Coupled drift: a novel term that describes selective pressure on a trait paired with random genetic drift. Selection can act symetrically or asymetrically resulting in different phenotypic variations (Tazzyman & Iwasa, 2010).
Case study: Strawberry Poison Dart-Frog[]
In a study by Tazzyman & Iwasa (2010), they investigated the role of female choice (intersexual selection) and color in the strawberry poison-dart frog Oophaga pumilio. In this species the females relies on the male to cooperatively raise their offspring. Color is also important, as this indicates to other animals that they are posinous. They compared this species with another colosely dart frog species that does not exhibit the same female choice reporoductive strategy. They found that the female choice was "coupled" with color as the secondary selective force). In this case various phyenodtypic polymorphisms have resulted from coupling of female choice (as it is driven mainly by genetic drift) and secondly by color.
References[]
Tazzyman, S., & Iwasa, Y. (2010). Sexual selection can increase the effect of random genetic drift--a quantitative genetic model of polymorphism in Oophaga pumilio, the strawberry poison-dart frog. Evolution; International Journal Of Organic Evolution, 64(6), 1719-1728. doi:10.1111/j.1558-5646.2009.00923.x