Van Homrigh Anna, Higgie Megan, McGuigan Katrina, Blows Mark W
School of Integrative Biology, University of Queensland, Brisbane, Australia.
Curr Biol. 2007 Mar 20;17(6):528-32. doi: 10.1016/j.cub.2007.01.055. Epub 2007 Feb 15.
Sexually selected traits display substantial genetic variance [1, 2], in conflict with the expectation that sexual selection will deplete it [3-5]. Condition dependence is thought to resolve this paradox [5-7], but experimental tests that relate the direction of sexual selection to the availability of genetic variance are lacking. Here, we show that condition-dependent expression is not sufficient to maintain genetic variance available to sexual selection in multiple male sexually selected traits. We employed an experimental design that simultaneously determined the quantitative genetic basis of nine male cuticular hydrocarbons (CHCs) of Drosophila bunnanda, the extent of condition dependence of these traits, and the strength and direction of sexual selection acting upon them. The CHCs of D. bunnanda are condition dependent, with 18% of the genetic variance in male body size explained by genetic variance in CHCs. Despite the presence of genetic variance in individual male traits, 98% of the genetic variance in CHCs was found to be orientated more than 88 degrees away from the direction of sexual selection and therefore unavailable to selection. A lack of genetic variance in male traits in the direction of sexual selection may represent a general feature of sexually selected systems, even in the presence of condition-dependent trait expression.
性选择的性状表现出显著的遗传变异[1,2]，这与性选择会耗尽遗传变异的预期相冲突[3-5]。条件依赖性被认为可以解决这一悖论[5-7]，但缺乏将性选择方向与遗传变异可用性联系起来的实验测试。在这里，我们表明，条件依赖性表达不足以维持多个雄性性选择性状中可用于性选择的遗传变异。我们采用了一种实验设计，同时确定了布氏果蝇九个雄性表皮碳氢化合物（CHCs）的数量遗传基础、这些性状的条件依赖程度，以及作用于它们的性选择的强度和方向。布氏果蝇的CHCs具有条件依赖性，雄性体型中18%的遗传变异可由CHCs中的遗传变异解释。尽管单个雄性性状存在遗传变异，但发现CHCs中98%的遗传变异与性选择方向的夹角超过88度，因此无法用于选择。即使存在条件依赖的性状表达，雄性性状在性选择方向上缺乏遗传变异可能是性选择系统的一个普遍特征。
