近日，中科院遗传与发育生物学研究所研究员John Speakman通过参与国际合作研究，解决了长久以来困扰科学界的一个谜团——企鹅为什么不会飞？该研究认为，企鹅高效的游泳和潜水行为可能提高了其飞行成本。相关研究日前发表于美国《国家科学院院刊》。
企鹅为什么在进化过程中丧失了飞行能力？相关原因一直以来都是个谜，因为不能飞行使得企鹅的一些行为看起来与环境不相适应。例如，为了从栖息地走到海边，帝企鹅通常会花上几天时间步行60公里，它们如果能飞的话，则只需要几个小时。
有一种观点认为，企鹅可能无法进化出既能飞行又能游泳和潜水的双翼，该假说被称为生物力学理论。据此理论，企鹅在进化过程中，双翼越来越适应游泳和潜水，但也使得其飞行成本越来越高，在某些时候，企鹅无法维持飞行的成本，因此就变得不再会飞。
为此，来自加拿大、美国、英国和中国的科学家组成联合小组，对海雀科的一种鸟类——海鸠进行了观察，他们发现，上述理论或可解释企鹅为什么不会飞。
海鸠是一种潜水和游泳行为与企鹅非常类似的海鸟，不同的是，海鸠仍然保留了飞行能力。该团队借助了一种叫做双标水的同位素技术，在用记录仪监控海鸠行为数据的同时检测了海鸠的能量消耗。
研究结果显示，海鸠潜水行为所需的能量低于其他鸟类，仅次于企鹅潜水行为的效率。但是，海鸠飞行行为所需的能量，是其基础代谢率的31倍，在所有有报道的飞行鸟类中是最高的。这种高效潜水和低效飞行行为的结合很好地印证了生物力学模型的预测。
该文章的第一作者，来自加拿大马尼托巴大学的研究生Kyle Elliott表示，很显然，野生动物的结构限制了其功能，动物会在两种不同生境的行为中采取折中的办法。（生物谷Bioon.com）
生物谷推荐英文摘要：
Proceedings of the National Academy of Sciences DOI：10.1073/pnas.1304838110
High flight costs, but low dive costs, in auks support the biomechanical hypothesis for flightlessness in penguins
Kyle H. Elliotta,1, Robert E. Ricklefsb,1, Anthony J. Gastonc, Scott A. Hatchd, John R. Speakmane,f, and Gail K. Davorena
Flight is a key adaptive trait. Despite its advantages, flight has been lost in several groups of birds, notably among seabirds, where flightlessness has evolved independently in at least five lineages. One hypothesis for the loss of flight among seabirds is that animals moving between different media face tradeoffs between maximizing function in one medium relative to the other. In particular, biomechanical models of energy costs during flying and diving suggest that a wing designed for optimal diving performance should lead to enormous energy costs when flying in air. Costs of flying and diving have been measured in free-living animals that use their wings to fly or to propel their dives, but not both. Animals that both fly and dive might approach the functional boundary between flight and nonflight. We show that flight costs for thick-billed murres (Uria lomvia), which are wing-propelled divers, and pelagic cormorants (Phalacrocorax pelagicus) (foot-propelled divers), are the highest recorded for vertebrates. Dive costs are high for cormorants and low for murres, but the latter are still higher than for flightless wing-propelled diving birds (penguins). For murres, flight costs were higher than predicted from biomechanical modeling, and the oxygen consumption rate during dives decreased with depth at a faster rate than estimated biomechanical costs. These results strongly support the hypothesis that function constrains form in diving birds, and that optimizing wing shape and form for wing-propelled diving leads to such high flight costs that flying ceases to be an option in larger wing-propelled diving seabirds, including penguins.
