Molecular Phylogenetics and the Evolution of Rattlesnakes [Crotalus and Sistrurus]

康奈尔大学的Kelly R. Zamudio博士和Harry W. Greene博士获得了一笔研究响尾蛇进化的资金。这28个物种包括一群生态多样化的新世界pitvipers，它们具有独特的摇尾肌肉和在它们改良的尾尖上发出声音的节段。尽管科学家和公众对它们有着广泛的兴趣，但在分子系统学的最新创新之前，人们已经对它们的起源和多样化做出了先前的推断。例如，没有证据表明人们普遍认为响尾蛇是对野牛群的反应而进化的，而且研究生物地理学和特征进化的新统计方法以前也没有应用于这一主题。Zamudio和Greene将对响尾蛇及其近亲的几个核基因和线粒体基因进行DNA测序，其直接目标是重建它们的关系和生物地理历史，然后测试响尾蛇起源的五种不同情况。响尾蛇在人类学、生态学、进化生物学、自然保护和生物医学研究中扮演着越来越重要的角色，Zamudio和Greene的发现将为这些主题提供重要的比较视角。响尾蛇是重要的捕食者，进化关系的知识将阐明物种形成和其他历史因素在构建自然群落中的作用。作为理解和最终治疗人类疾病的暗示的例子，因为它们表现出父母的照顾，而不是因为喂养幼崽而变得复杂，雌性响尾蛇为研究这种行为的激素控制提供了一个简单的模型系统。同样，摇肌在解剖学和生理学上都类似于心脏组织，近年来，用核磁共振和其他活体技术研究完整生物体内的肌肉生物化学，证明了受约束的活响尾蛇的尾巴非常有用。了解响尾蛇的进化关系将使研究人员能够战略性地选择具有或缺乏特定特征的物种，从而理清正常和异常功能发展背后的分子机制。

A grant has been awarded to Dr. Kelly R. Zamudio and Dr. Harry W. Greene at Cornell University to study rattlesnake evolution. The 28 species comprise a group of ecologically diverse New World pitvipers with unique tail shaker muscles and noise-making segments on their modified tail tips. Despite widespread interest by scientists and the public, previous inferences about their origin and diversification were made prior to recent innovations in molecular systematics. No evidence exists for a widespread belief that rattles evolved in response to bison herds, for example, and new statistical approaches for studying biogeography and character evolution have not previously been applied to this topic. Zamudio and Greene will sequence the DNA in several nuclear and mitochondrial genes of rattlesnakes and their relatives, with the immediate goals of reconstructing their relationships and biogeographic history, then testing five alternative scenarios of rattle origin. Rattlesnakes play increasingly prominent roles in anthropology, ecology, evolutionary biology, conservation, and biomedical research, topics on which Zamudio and Greene's findings will provide important comparative perspectives. Rattlesnakes are important predators and knowledge of evolutionary relationships will elucidate the roles of speciation and other historical factors in structuring natural communities. As examples of implications for understanding and eventually treating human diseases, because they exhibit parental care that is not complicated by the feeding of young, female rattlesnakes offer a simple model system for studying hormonal control of that behavior. Likewise, the shaker muscle anatomically and physiologically resembles heart tissue, and in recent years the tails of restrained, live rattlesnakes have proved extremely useful for studying muscle biochemistry in intact organisms with NMR and other in vivo techniques. Understanding rattlesnake evolutionary relationships will enable researchers to strategically choose species that have or lack particular characteristics, and thereby untangle the molecular mechanisms underlying the development of normal and abnormal functions.