DISSERTATION RESEARCH: Species Boundaries and Phylogenetic Relationships in Chromosome Races of the Sceloporus grammicus Complex (Squamata).

美国国家科学基金会向杨百翰大学的Jack Sites博士和jonathan Marshall先生提供了一项资助，用于研究“墨西哥中部Sceloporus grammicus复合体蜥蜴染色体种族的物种边界和系统发育关系”。这些蜥蜴代表了所有非哺乳动物脊椎动物群体中染色体变异最大的一种，它们被描述为染色体突变如何促进物种形成过程的教科书范例。Sites博士花了20多年的研究生涯来研究这一群体的物种形成机制，并积累了足够大的数据库，使这些蜥蜴成为选择研究的“模型系统”。这项研究的目的将是使用至少四种不同的方法，测试墨西哥中部已知的八个染色体“种族”的物种边界。这将通过分析三种不同的遗传标记、染色体、凝胶电泳分析的酶产物和来自三个基因区域的DNA序列来完成。方法和数据集之间的一致性将用于推断物种边界，这应该允许确定方法之间任何可能冲突的原因。本研究在以下背景下具有广泛的意义。系统生物学经常提出的两个目标是：(1)发现现存物种的主要“自然类群”（=枝）以及它们之间的关系；(2)发现物种。在系统生物学中，关于实现目标1的树重建理论和方法的文献非常多，但在目标2方面却令人惊讶地有限，尽管物种划分问题现在越来越受到关注。迄今为止，只发表了一项研究，比较了几种方法（三种）的性能，但数据集有限，Sites和Marshall可以利用S. grammicus复合物的大型数据库，远远超出以往的任何尝试，并为物种划分的更大争论做出贡献。

A grant has been awarded from the National Science Foundation to Dr. Jack Sites and Mr. Jonathon Marshall, Brigham Young University, to study "Species boundaries and phylogenetic relationships of chromosome races of lizards of the Sceloporus grammicus complex in central Mexico." These lizards represent one of the most chromosomally variable of all non-mammalian vertebrate groups, and they have been described as textbook examples of how chromosomal mutations may facilitate the speciation process. Dr. Sites has spent over two decades of his research career studying speciation mechanisms in this group, and has accumulated a sufficiently large data base to make these lizards a "model system" for selected kinds of research. The objective of this study will be to test species boundaries across the eight chromosome 'races' known from central Mexico, using a minimum of four different methodologies. This will be accomplished by analyzing three different kinds of genetic markers, chromosomes, enzyme products analyzed by gel electrophoresis, and DNA sequences from three gene regions. Concordance among methods and data sets will be used to infer species boundaries, which should allow determination of causes for any possible conflicts among methods. This study has broad implications in the following context. Two frequently stated objectives of systematic biology are to: (1) discover the major 'natural groups' (= clades) of living species and how these are related, and (2) to discover species. The literature in systematic biology is very large with respect to theory and methods of tree-reconstruction to accomplish objective 1, but it is surprising limited with respect to objective 2, although the issue of delimitation of species is now getting increased attention. To date only a single study has been published comparing the performance of several methods (three), but the data set was limited, and Sites and Marshall can capitalize on the large data base for the S. grammicus complex to go far beyond anything previously attempted, and to contribute to the larger debate on delimiting species.