Department of Biology, University of South Dakota, Vermillion, SD, USA.
J Evol Biol. 2013 Jun;26(6):1281-93. doi: 10.1111/jeb.12133. Epub 2013 Mar 5.
Exaggerated male ornaments are predicted to be costly to their bearers, but these negative effects may be offset by the correlated evolution of compensatory traits. However, when locomotor systems, such as wings in flying species, evolve to decrease such costs, it remains unclear whether functional changes across related species are achieved via the same morphological route or via alternate changes that have similar function. We conducted a comparative analysis of wing shape in relation to eye-stalk elongation across 24 species of stalk-eyed flies, using geometric morphometrics to determine how species with increased eye span, a sexually selected trait, have modified wing morphology as a compensatory mechanism. Using traditional and phylogenetically informed multivariate analyses of shape in combination with phenotypic trajectory analysis, we found a strong phylogenetic signal in wing shape. However, dimorphic species possessed shifted wing veins with the result of lengthening and narrowing wings compared to monomorphic species. Dimorphic species also had changes that seem unrelated to wing size, but instead may govern wing flexion. Nevertheless, the lack of a uniform, compensatory pattern suggests that stalk-eyed flies used alternative modifications in wing structure to increase wing area and aspect ratio, thus taking divergent morphological routes to compensate for exaggerated eye stalks.
夸张的雄性装饰物预计对其佩戴者来说是有代价的，但这些负面影响可能会被相关的补偿特征的进化所抵消。然而，当运动系统（如飞行物种的翅膀）进化以降低这些成本时，尚不清楚相关物种的功能变化是通过相同的形态途径还是通过具有相似功能的替代变化来实现的。我们使用几何形态测量学，对 24 种眼柄蝇进行了翅膀形状与眼柄伸长的比较分析，以确定具有增加的眼距（一种性选择特征）的物种如何作为一种补偿机制来改变翅膀形态。通过传统和基于系统发育的形状多元分析以及表型轨迹分析，我们发现翅膀形状具有很强的系统发育信号。然而，二态性物种的翅膀静脉发生了变化，与单态性物种相比，翅膀变长变窄。二态性物种的翅膀还有一些与翅膀大小无关的变化，而这些变化可能会影响翅膀的弯曲。然而，缺乏统一的、补偿性的模式表明，眼柄蝇在增加翅膀面积和纵横比方面使用了替代的翅膀结构修饰，从而采取了不同的形态途径来补偿夸张的眼柄。
