一个与人类语言进化相关的基因可能同时帮助蝙蝠喊出了自己的声音。根据一项新的研究，为了寻找猎物及躲避障碍物，不同种类的蝙蝠都会发出高频尖叫声，无一例外，它们都携带有一种高度变异的FOXP2基因，这意味着，这种基因在蝙蝠体内的遗传变化促进了其在功能上的进化。
FOXP2所编码的蛋白质似乎能够影响嘴部运动和语言能力之间的协调性。2001年，这种基因第一次引起了科学家的关注——人们发现，它与说话和语言紊乱有关。一年后，研究人员再度发现，FOXP2很可能在语言的进化中扮演了一个重要角色。这种基因同时也对小鼠产生了影响：那些没有FOXP2的小鼠彼此之间无法利用超声波进行交流。
英国伦敦大学女王学院的遗传学家Stephen Rossiter和他的同事于是寻思，蝙蝠的进化是否也依赖于FOXP2基因。相形之下，这些哺乳动物使人类的会话多少显得有些小儿科——在一种名为回声定位的行为中，蝙蝠必须使鼻、口、耳和喉协同工作，以便发出叫声和接收回声。所有这些过程都是在飞行过程中机动完成的，而蝙蝠也正是依靠这些信号为自己导航。Rossiter与中国上海华东师范大学的李钢（音译）和张树义及其同事合作，对13只蝙蝠（它们分属6类蝙蝠）所携带的FOXP2基因进行了测序，这些蝙蝠有的使用回声定位，有的则没有这种技能。研究人员同时在其他23种哺乳动物——其中包括鸭嘴兽——以及2种鸟类和1种爬行动物体内寻找这种基因。
研究人员发现，与其他动物相比，蝙蝠的FOXP2基因序列所产生的突变是前者的2倍，这意味着迅速的进化。此外，亲缘关系较近的蝙蝠——它们具有类似的超声波接受能力——趋向于发生相同的突变。同时，这些遗传变化并不会被那些亲缘关系较远或不依靠回声定位的蝙蝠所共享。某些蝙蝠具有与导致人类语言障碍的变异类似的遗传突变。Rossiter指出：“我们的发现表明，FOXP2基因在蝙蝠的回声定位能力的进化与多样化过程中扮演了一个至关重要的角色。”
这一结论对于英国牛津大学的神经遗传学家Simon Fisher具有重要意义，他曾发现FOXP2变异与语言紊乱之间存在联系。Fisher表示，这一研究结果支持了这样一种假设，即源自动物祖先发声与运动系统的说话和语言的进化，随着时间流逝被重新排列，且变得更为复杂。但德国柏林自由大学的神经生物学家Constance Scharff强调，对于FOXP2基因在回声定位中扮演的角色还需要进行功能性研究，例如搞清敲掉这一基因后会产生什么样的后果。（科学时报）
原始出处:
Received: March 18, 2007; Accepted: August 15, 2007; Published: September 19, 2007
Accelerated FoxP2 Evolution in Echolocating Bats
Gang Li1,2, Jinhong Wang1, Stephen J. Rossiter3*, Gareth Jones4, Shuyi Zhang1*
1 School of Life Science, East China Normal University, Shanghai, China, 2 Institute of Zoology and Graduate University, Chinese Academy of Sciences, Beijing, China, 3 School of Biological and Chemical Sciences, Queen Mary, University of London, London, United Kingdom, 4 School of Biological Sciences, University of Bristol, Bristol, United Kingdom
Abstract
FOXP2 is a transcription factor implicated in the development and neural control of orofacial coordination, particularly with respect to vocalisation. Observations that orthologues show almost no variation across vertebrates yet differ by two amino acids between humans and chimpanzees have led to speculation that recent evolutionary changes might relate to the emergence of language. Echolocating bats face especially challenging sensorimotor demands, using vocal signals for orientation and often for prey capture. To determine whether mutations in the FoxP2 gene could be associated with echolocation, we sequenced FoxP2 from echolocating and non-echolocating bats as well as a range of other mammal species. We found that contrary to previous reports, FoxP2 is not highly conserved across all nonhuman mammals but is extremely diverse in echolocating bats. We detected divergent selection (a change in selective pressure) at FoxP2 between bats with contrasting sonar systems, suggesting the intriguing possibility of a role for FoxP2 in the evolution and development of echolocation. We speculate that observed accelerated evolution of FoxP2 in bats supports a previously proposed function in sensorimotor coordination.
Figure 1. Radial phylogenetic tree showing relative rates of non-synonymous evolution among 35 eutherian mammals, including 13 bats.
Bats species are given as italicised binomial names. Branch lengths based on maximum-likelihood estimates of non-synonymous substitutions along 1995 bp of the FoxP2 gene are superimposed onto a cladogram based on published trees [31], [33], [34]. Bat lineages are coloured to show the echolocating Yinpterochiroptera (blue) that mostly possess high duty constant frequency (CF) calls with at least partial Doppler shift compensation, the Yangochiroptera (orange) that mostly possess low duty cycle calls, as well as the absence of laryngeal echolocation in Yinpterochiroptera fruit bats (violet). The taxa analysed are listed in the Methods and in table S2
全文链接：http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000900
