Askew Graham N
Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
J Exp Biol. 2014 Sep 15;217(Pt 18):3237-41. doi: 10.1242/jeb.107474.
One of the classic examples of an exaggerated sexually selected trait is the elaborate plumage that forms the train in male peafowl Pavo cristatus (peacock). Such ornaments are thought to reduce locomotor performance as a result of their weight and aerodynamic drag, but this cost is unknown. Here, the effect that the train has on take-off flight in peacocks was quantified as the sum of the rates of change of the potential and kinetic energies of the body (P(CoM)) in birds with trains and following the train's removal. There was no significant difference between P(CoM) in birds with and without a train. The train incurs drag during take-off; however, while this produces a twofold increase in parasite drag, parasite power only accounts for 0.1% of the total aerodynamic power. The train represented 6.9% of body weight and is expected to increase induced power. The absence of a detectable effect on take-off performance does not necessarily mean that there is no cost associated with possessing such ornate plumage; rather, it suggests that given the variation in take-off performance per se, the magnitude of any effect of the train has little meaningful functional relevance.
夸张的性选择特征的经典例子之一是雄性孔雀（孔雀属印度孔雀）尾羽上形成尾屏的精致羽毛。由于其重量和空气动力学阻力，这种装饰物被认为会降低运动性能，但这种代价尚不清楚。在这里，尾屏对孔雀起飞飞行的影响被量化为有尾屏的鸟类以及尾屏移除后鸟类身体质心（P(CoM)）的势能和动能变化率之和。有尾屏和无尾屏的鸟类的P(CoM)之间没有显著差异。尾屏在起飞时会产生阻力；然而，虽然这会使寄生阻力增加两倍，但寄生功率仅占总空气动力功率的0.1%。尾屏占体重的6.9%，预计会增加诱导功率。对起飞性能没有可检测到的影响并不一定意味着拥有这种华丽羽毛没有代价；相反，这表明鉴于起飞性能本身的变化，尾屏的任何影响的大小几乎没有有意义的功能相关性。
