Migrate small, sound big: functional constraints on body size promote tracheal elongation in cranes
Migrate small, sound big: functional constraints on body size promote tracheal elongation in cranes
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DOI：
10.1111/jeb.12397
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发表时间：
2014-06-01
影响因子：
2.1
通讯作者：
Witt, C. C.
中科院分区：
文献类型：
--
作者：
Jones, M. R.;Witt, C. C.
有机体特征通常代表相反选择压力的结果。尽管社会或性选择可以导致限制功能或生存的特征（例如观赏羽毛）的进化，但尚不清楚选择的强度和方向如何响应增加限制严重性的生态变化。例如，自然选择可能会导致体型减小，以提高候鸟的飞行性能，但有利于体型较大的社会或性选择可能会产生反作用力。气管伸长是这些相反压力的潜在结果，因为它使鸟类能够传达夸大身体尺寸的听觉信号。我们预测，鹤的迁徙进化与体型的减小同时发生，同时伴随着通过气管伸长对明显体型较大的社会或性选择的强化。我们采用系统发育比较方法来研究鹤的迁徙距离、体重和气管长度之间的关系。正如预测的那样，我们发现迁移距离与体型呈负相关，与比例气管长度呈正相关。这一结果与我们的假设一致，即身体尺寸的进化减小导致了对气管长度的强化选择。气管长度积极选择加剧的最可能的最终原因是在种内竞争和领地竞争中传递大体型的直接好处。我们得出的结论是，社会或性选择对鹤体型大小的影响与功能限制的程度有关。
Organismal traits often represent the outcome of opposing selection pressures. Although social or sexual selection can cause the evolution of traits that constrain function or survival (e.g. ornamental feathers), it is unclear how the strength and direction of selection respond to ecological shifts that increase the severity of the constraint. For example, reduced body size might evolve by natural selection to enhance flight performance in migratory birds, but social or sexual selection favouring large body size may provide a countervailing force. Tracheal elongation is a potential outcome of these opposing pressures because it allows birds to convey an auditory signal of exaggerated body size. We predicted that the evolution of migration in cranes has coincided with a reduction in body size and a concomitant intensification of social or sexual selection for apparent large body size via tracheal elongation. We used a phylogenetic comparative approach to examine the relationships among migration distance, body mass and trachea length in cranes. As predicted, we found that migration distance correlated negatively with body size and positively with proportional trachea length. This result was consistent with our hypothesis that evolutionary reductions in body size led to intensified selection for trachea length. The most likely ultimate causes of intensified positive selection on trachea length are the direct benefits of conveying a large body size in intraspecific contests for mates and territories. We conclude that the strength of social or sexual selection on crane body size is linked to the degree of functional constraint.