REU: Phylogenetic Relationships, Population Structure, and Hybrid Zone Dynamics Among Central Mexico Chromosome Races of the Sceloporus grammicus Complex (Iguanidae)

这项研究是由杨百翰大学的赛斯博士和德克萨斯农工大学的艾拉·格林鲍姆和斯科特·戴维斯共同完成的，研究的三个主要目标与墨西哥中部梅斯奎特蜥蜴的进化史有关。首先，将使用几种分子技术(蛋白质和重组DNA)来测试基于染色体的假设，即来自墨西哥中部的七个已知染色体小种(具有不同染色体数量的形态相似的蜥蜴种群)的进化关系。在这些种族中重建染色体进化的模式取决于从独立于染色体的数据集了解它们的关系--这就是分子标记的原因。密切相关的第二个目标将是评估其中两个小种内的基因量，再次使用分子标记，以确定新的染色体突变可能持续并最终传播到整个染色体小种范围的可能性。这项工作的第三个方面将是详细研究在有限范围内相遇和杂交的两个染色体种族之间的基因流模式。第二个目标也将为这项混合区研究提供内部“控制”。通过比较杂交动物性细胞中的染色体行为与杂交区外的纯“亲本”染色体小种中的染色体行为，我们可以确定染色体差异在造成杂交动物部分不育中所起的作用，从而有助于减少基因流。如果发生这种情况，染色体的变化可能会导致遗传分化，以至于染色体种族成为不同的物种。

This study, by Dr. Sites at Brigham Young University and Ira Greenbaum and Scott Davis at Texas A&M University, has three major objectives relating to the evolutionary history of the mesquite lizard, Sceloporus grammicus, in central Mexico. First, several molecular techniques (protein and recombinant DNA) will be used to test a chromosomally-based hypothesis of the evolutionary relationships of seven known chromosome races (populations of morphologically similar lizards with different chromosome numbers) from central Mexico. Reconstructing the patterns of chromosomal evolution in these races depends upon knowing their relationships from data sets independent of the chromosomes--hence the reason for the molecular markers. A closely related second objective will be to assess the amount of gene flow within two of these races, again using the molecular markers, to determine the likelihood with which a new chromosomal mutation may persist and eventually be spread throughout the range of the chromosome race. The third aspect of this work will be the detailed study of patterns of gene flow between two chromosome races that meet and hybridize in a limited part of their range. The second objective will also provide an internal "control" for this hybrid zone study. By comparing chromosome behavior in the sex cells of hybrid animals relative to that in pure "parental" chromosome races outside of the zone of hybridization, we can determine the role played by chromosomal differences in causing partial sterility in the hybrids and thereby contributing to a reduction of gene flow. If this occurs, the chromosomal changes may foster genetic divergence to the point that the chromosome races become distinct species.