Am Nat. 2020 Dec;196(6):775-784. doi: 10.1086/711416. Epub 2020 Oct 30.
AbstractComplex features, such as vision, limbs, and flight, have been lost by many groups of animals. Some groups of birds are more prone to loss of flight than others, but few studies have investigated possible reasons for this variation. I tested the hypothesis that a rare strategy of flight feather replacement is involved in rate variation in the evolution of flightlessness in birds. This strategy involves a simultaneous molt of the flight feathers of the wing, resulting in a temporary flightless condition during molt. I hypothesized that adaptations for this flightless period may serve as preadaptations for permanent flightlessness under conditions that favor permanent loss of flight. I found an elevated rate of loss of flight in lineages with simultaneous wing molt compared with loss of flight in lineages without simultaneous wing molt. This may indicate that birds with simultaneous molt are more prepared to adjust quickly to open niches that do not require flight, such as terrestrial niches on island habitats. These results illustrate how molt strategies can influence the long-term evolutionary trajectories of birds and provide insight into how phenotypic precursors may act as a mechanism of rate variation in the loss of complex traits.
许多动物群体已经失去了复杂的特征，如视力、肢体和飞行。一些鸟类群体比其他群体更容易失去飞行能力，但很少有研究调查这种变化的可能原因。我测试了一个假设，即一种罕见的飞行羽毛更换策略可能与鸟类丧失飞行能力的进化速度有关。这种策略涉及翅膀的飞行羽毛同时脱落，导致在换羽期间暂时失去飞行能力。我假设，适应这种无飞行期的特征可能是在有利于永久丧失飞行能力的条件下，为永久性丧失飞行能力提供的预先适应。我发现，与没有同时进行翅膀脱落的谱系相比，具有同时进行翅膀脱落的谱系中丧失飞行能力的速度更快。这可能表明，具有同时换羽的鸟类更能迅速适应不需要飞行的开放生态位，例如岛屿栖息地的陆地生态位。这些结果说明了换羽策略如何影响鸟类的长期进化轨迹，并深入了解表型前体如何作为丧失复杂特征的速度变化的机制。
