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

San Diego State University Foundation, San Diego CA

Investigators

Abstract

0108484 Reeder 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).