Evolution of the North American Whiptail Lizards (Teiidae: Cnemidophorus) and Re-evaluation of Unisexual Origins: A Multi-genic Approach

0108484Reeder Whitails(Cnemidophorus属)隶属于蜥蜴科。惠普塔广泛分布在整个新大陆，从美国向南延伸到阿根廷。然而，它们最大的多样性是在美国西南部和墨西哥的干旱和半干旱地区，在那里它们是爬行动物区系中显著的组成部分。惠氏蜥蜴是一个重要的生态类群，大量的生态和生活史研究反映了这一点。惠普尾一直是被研究最广泛的蜥蜴群体之一，仅次于刺蜥蜴(Scelopus)和栅栏蜥蜴(Anolis)。除了它们的丰度和地理上与北美生物学家的接近之外，惠普塔被深入研究的另一个原因是出现了孤雌生殖的全雌性物种(可能是杂交起源)。大约三分之一的物种是单性的，其中大多数全是雌性的物种(=单性)生活在美国西南部和墨西哥北部。虽然人们已经对惠普尾进行了广泛的研究，对它们的生物学、生态学和自然历史也有了很多了解，但人们对惠普塔之间的系统发育关系仍然知之甚少。此外，在墨西哥北部，关于三个主要物种复合体内的物种限制也存在许多混淆。许多种群不能被分配给当前的亚种或物种。目前尚不清楚这种混淆是由于某些分类群之间的广泛杂交造成的，还是存在新的、未描述的分类群。最后，尽管生物学家已经花费了一些努力来研究这个群体中单性恋的起源，但许多血统的母系和父系的祖先仍然是模棱两可的。DNA序列数据可以用来解决这些问题，如系统发育、物种限制和北美惠普塔种群内的单性起源。然而，在收集分子数据之前，仍然需要许多双性和单性鞭尾种群和/或物种的组织样本。圣地亚哥州立大学的托德·里德博士和他的同事禤浩焯博士将在美国西南部和墨西哥进行广泛的实地考察，以获取必要的组织样本。样本将从基本上所有的北美双性和单性鞭尾分类群中收集。一旦组织可用，DNA序列数据将从快速进化的线粒体和核基因中收集。除了解决鞭尾系统发育、物种限制和单性起源方面的具体问题外，这项研究的结果还具有更广泛的科学意义。鞭尾系统发育可用于利用现代比较/系统发育方法重新评估有关鞭尾的大量生物学/生态数据，并为这一不同类群的进化提供新的见解。单性在其他动物群体中也存在；因此，将产生更多关于自然界中单性的起源和持久性的背景数据。这将是使用快速进化的核内含子序列来研究杂交和物种形成的首批研究之一。因此，这项研究将测试这些基因区域在解决进化生物学家长期感兴趣的这些领域中的问题的实用性。本科生和研究生将参与这个项目的各个方面。学生将在现代领域和实验室技术方面获得宝贵的经验，学习进化生物学和系统生物学的基本概念，并获得展示研究成果的技能(通过口头陈述和书面手稿)。

0108484Reeder Whiptails (genus Cnemidophorus) belong to the lizard family Teiidae. Whiptails range widely throughout the New World, extending from the U.S. southward to Argentina. However, their greatest diversity is in the arid and semi-arid regions of the Southwest U.S. and Mexico where they are a conspicuous component of the reptile fauna. Whiptails are an ecologically important lizard group, which is reflected by numerous ecological and life history studies. Whiptails have been one of the most extensively studied group of lizards, third only to Sceloporus (spiny and fence lizards) and Anolis (anoles). Besides their abundance and geographic proximity to North American biologists, another reason whiptails have been intensively studied is the occurrence of parthenogenetic all-female species (of likely hybrid origin). Approximately one third of the species are unisexual, with the majority of these all-female species (=unisexuals) occurring in the southwestern U.S. and northern Mexico. While whiptails have been extensively studied and much is known about their biology, ecology, and natural history, the phylogenetic relationships among whiptails is still poorly understood. Also, in northern Mexico, much confusion exists regarding the species limits within three major species complexes. Many populations cannot be allocated to current subspecies or species. It is unclear whether the confusion arises from extensive hybridization between some taxa or whether new, undescribed taxa exist. And finally, while biologists have spent some effort studying the origins of the unisexuals in this group, the maternal and paternal ancestry of many lineages is still ambiguous. DNA sequence data can be used to address these issues of phylogeny, species limits, and unisexual origins within the North American group of whiptails. However, before molecular data can be collected, tissue samples are still needed from many bisexual and unisexual whiptail populations and/or species. Extensive fieldwork will be conducted in the Southwest U.S. and Mexico by Dr. Tod Reeder of San Diego State University and his colleague Dr. Adrian Nieto Montes de Oca in Mexico, to obtain the necessary tissue samples. Samples will be collected from essentially all North American bisexual and unisexual whiptail taxa. Once tissues are available, DNA sequence data will be gathered from rapidly evolving mitochondrial and nuclear genes. Besides addressing specific issues in whiptail phylogeny, species limits, and unisexual origins, the results of this research have broader scientific significance. The whiptail phylogeny can be used to re-evaluate the extensive biological/ecological data on whiptails using modern comparative/phylogenetic approaches and provide new insights on the evolution of this diverse group. Unisexuals occur in other animal groups; thus, more background data will be generated on the origins and persistence of unisexuals in nature. This will be one of the first studies to use rapidly evolving nuclear intron sequences to study hybridization and speciation. Thus, this study will test the utility of these gene regions for addressing issues in these areas that have been of long interest to evolutionary biologists. Undergraduate and graduate students will be involved in all aspects of this project. Students will gain valuable experience in modern field and laboratory techniques, learn basic concepts in evolutionary and systematic biology, and acquire skills in the presentation of research results (through oral presentation and written manuscripts).