Male ornaments and other sex‐specific traits present some of the most dramatic examples of evolutionary innovations. Comparative studies of similar but independently evolved traits are particularly important for identifying repeated patterns in the evolution of these traits. Male‐specific modifications of the front legs have evolved repeatedly in Drosophilidae and other Diptera. The best understood of these novel structures is the sex comb of Drosophila melanogaster and its close relatives. Here, we examine the evolution of another male foreleg modification, the sex brush, found in the distantly related Drosophila immigrans species group. Similar to the sex comb, we find that the origin of the sex brush correlates with novel, spatially restricted expression of the doublesex (dsx) transcription factor, the primary effector of the Drosophila sex determination pathway. The diversity of Dsx expression patterns in the immigrans species group closely reflects the differences in the presence, position, and size of the sex brush. Together with previous work on sex comb evolution, these observations suggest that tissue‐specific activation of dsx expression may be a common mechanism responsible for the evolution of sexual dimorphism and particularly for the origin of novel male‐specific ornaments.

中文翻译：

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不断发展的doublesex表达与果蝇属物种组中男性性装饰品的起源和多样化有关。

男性饰品和其他特定性别特征是进化创新中最引人注目的例子。相似但独立进化的性状的比较研究对于确定这些性状进化中的重复模式尤为重要。在果蝇科和其他双翅类动物中，前腿的男性特定修饰反复发生。这些新颖结构的最佳理解是果蝇及其近亲的性梳。在这里，我们研究了在远缘的果蝇种群中发现的另一种雄性前肢修饰的进化，即性刷。与性梳类似，我们发现性刷的起源与新出现的空间受限表达有关doublesex（dsx）转录因子，果蝇性别决定途径的主要效应物。移民种组中Dsx表达模式的多样性密切反映了性刷的存在，位置和大小的差异。结合先前有关性梳进化的研究，这些观察结果表明，dsx表达的组织特异性激活可能是导致性二态性进化的主要机制，尤其是新型男性特异性装饰物的起源。