蝙蝠是翼手目动物的通称，是唯一演化出具有真正飞行能力的哺乳动物。跟鸟类进化出飞行能力一样，蝙蝠飞行能力的进化需要一系列十分复杂的形态和生理变化，因此达尔文在《物种起源》中感叹“从不能飞的原始哺乳动物进化为能飞的蝙蝠是不可思议的”。
中国科学院昆明动物研究所张亚平院士及其指导的博士生沈永义注意到飞行消耗的能量是奔跑3-15倍。因此，飞行除了需要骨骼等形态变化外，还需要能量供应系统的高效率化，以便能适应能量需求的急剧增加。通俗的比喻就是飞机能飞，不单单需要机翼等形态结构，还需要有强大的发动机来提供动力。线粒体是细胞的能量工厂，通过氧化呼吸链提供了生物体95%的能量，是动物各种运动所需能量动力的“发动机”。因此他们推测线粒体产能系统的进化应该与蝙蝠飞行能力的起源密切相关。通过全基因组比较分析，他们证实在蝙蝠飞行能力的起源过程中，线粒体的氧化呼吸链基因受到正选择，线粒体与细胞核编码的基因发生协同进化，以适应飞行起源过程中对能量需求的急剧增加。
该研究成果于4月26日在国际著名刊物美国《国家科学院院刊》（PNAS）在线发表。美国科学院院士David M. Hillis评价道：“该研究十分出色且令人兴奋，该研究结果对了解线粒体的分子生物学和进化，以及飞行的分子适应机制有广泛的意义”。
有趣的是，该研究团队2009年通过对飞行能力健全与退化的鸟类的比较研究，在Genome Research发表的姐妹篇工作揭示，线粒体基因组的选择压力与动物运动能力密切相关。
相关阅读：Genome Research：线粒体基因组的选择压力与动物运动能力相关
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.0912613107
Adaptive evolution of energy metabolism genes and the origin of flight in bats
Yong-Yi Shena,b,c, Lu Lianga,c, Zhou-Hai Zhub, Wei-Ping Zhoua,d, David M. Irwine,f, and Ya-Ping Zhanga,b,1
Bat flight poses intriguing questions about how flight independently developed in mammals. Flight is among the most energy-consuming activities. Thus, we deduced that changes in energy metabolism must be a primary factor in the origin of flight in bats. The respiratory chain of the mitochondrial produces 95% of the adenosine triphosphate (ATP) needed for locomotion. Because the respiratory chain has a dual genetic foundation, with genes encoded by both the mitochondrial and nuclear genomes, we examined both genomes to gain insights into the evolution of flight within mammals. Evidence for positive selection was detected in 23.08% of the mitochondrial-encoded and 4.90% of nuclear-encoded oxidative phosphorylation (OXPHOS) genes, but in only 2.25% of the nuclear-encoded nonrespiratory genes that function in mitochondria or 1.005% of other nuclear genes in bats. To address the caveat that the two available bat genomes are of only draft quality, we resequenced 77 OXPHOS genes from four species of bats. The analysis of the resequenced gene data are in agreement with our conclusion that a significantly higher proportion of genes involved in energy metabolism, compared with background genes, show evidence of adaptive evolution specific on the common ancestral bat lineage. Both mitochondrial and nuclear-encoded OXPHOS genes display evidence of adaptive evolution along the common ancestral branch of bats, supporting our hypothesis that genes involved in energy metabolism were targets of natural selection and allowed adaptation to the huge change in energy demand that were required during the origin of flight.
