Llopart Anna, Elwyn Susannah, Coyne Jerry A
Department of Ecology and Evolution, University of Chicago, Illinois 60637, USA.
Nature. 2002 Sep 26;419(6905):360; discussion 360. doi: 10.1038/419360a.
Many species of the fruitfly Drosophila are either sexually dimorphic for abdominal pigmentation (the posterior segments in males are black and those of females have thin dark stripes) or sexually monomorphic for this pigmentation (both sexes show striping). Kopp et al. report a correlation in two Drosophila clades between the expression of the bric-à-brac (bab) gene, which represses male-specific pigmentation in D. melanogaster females, and the presence of sexually dimorphic pigmentation. They suggest that sexual selection acted to produce sexual dichromatism in Drosophila by altering the regulation of bab, on the grounds that D. melanogaster males show a strong mate preference for females with lightly pigmented abdomens, and that this discrimination helps to maintain sexual dichromatism by preventing males from wasting time by courting other (darkly pigmented) males. Here we show that the mate discrimination observed by Kopp et al. may in fact have resulted from the nature of the strains and comparisons they used in their study and so could be irrelevant to mate choice in nature.
果蝇属的许多物种在腹部色素沉着方面要么具有性别二态性（雄性的后段为黑色，雌性的后段有细的深色条纹），要么在这种色素沉着方面具有性别单态性（两性都有条纹）。科普等人报告说，在两个果蝇进化枝中，抑制黑腹果蝇雌性中雄性特异性色素沉着的bric-à-brac（bab）基因的表达与性别二态性色素沉着的存在之间存在相关性。他们认为，性选择通过改变bab的调控作用于果蝇产生性二态色，理由是黑腹果蝇雄性对腹部色素较浅的雌性表现出强烈的配偶偏好，并且这种区分有助于通过防止雄性浪费时间向其他（色素较深的）雄性求爱来维持性二态色。在这里，我们表明科普等人观察到的配偶区分实际上可能是由于他们研究中使用的菌株和比较的性质所致，因此可能与自然中的配偶选择无关。
