Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada.
Department of Biology, Florida State University, Tallahassee, Florida, 32306.
Evolution. 2021 May;75(5):1117-1131. doi: 10.1111/evo.14200. Epub 2021 Apr 6.
Sexual dimorphism is widely viewed as adaptive, reflecting the evolution of males and females toward divergent fitness optima. Its evolution, however, may often be constrained by the shared genetic architecture of the sexes, and by allometry. Here, we investigated the evolution of sexual size dimorphism, shape dimorphism, and their allometric relationship, in the wings of 82 taxa in the family Drosophilidae that have been diverging for at least 33 million years. Shape dimorphism among species was remarkably similar, with males characterized by longer, thinner wings than females. There was, however, quantitative variation among species in both size and shape dimorphism, with evidence that they have adapted to different evolutionary optima in different clades on timescales of about 10 million years. Within species, shape dimorphism was predicted by size, and among species, there was a strong relationship between size dimorphism and shape dimorphism. Allometry constrained the evolution of shape dimorphism for the two most variable traits we studied, but dimorphism was evolutionary labile in other traits. The keys for disentangling alternative explanations for dimorphism evolution are studies of natural and sexual selection, together with a deeper understanding of how microevolutionary parameters of evolvability relate to macroevolutionary patterns of divergence.
性二型性被广泛认为是适应性的，反映了男性和女性朝着不同的适应最优方向进化。然而，它的进化可能经常受到性别共享遗传结构和异速生长的限制。在这里，我们研究了至少 3300 万年来一直在分化的果蝇科 82 个分类群的翅膀的性大小二型、形状二型及其异速生长关系。物种之间的形状二型性非常相似，雄性的翅膀比雌性的更长、更薄。然而，大小和形状二型性在物种之间存在定量变化，有证据表明它们在不同的进化枝中适应了不同的进化最优值，时间尺度约为 1000 万年。在种内，形状二型性由大小预测，而在种间，大小二型性和形状二型性之间存在很强的关系。异速生长限制了我们研究的两个最具可变性特征的形状二型性的进化，但在其他特征中，二型性是进化不稳定的。解开二型性进化替代解释的关键是对自然选择和性选择的研究，以及更深入地了解可进化性的微观进化参数与宏观进化分歧模式之间的关系。
