DISSERTATION RESEARCH: Phylogeny of the Genus Microlophus (Squamata: Tropiduridae): A History of Colonization and Dispersal

美国国家科学基金会向杨百翰大学的杰克·赛斯博士和埃德加·贝纳维德斯先生提供了一笔赠款，用于研究“南美蜥蜴属小蜥蜴的系统发育”。该属由22个已知种组成，地理分布极为罕见；9个种仅分布在东太平洋厄瓜多尔西海岸约1000公里处的加拉帕戈斯群岛，其余13个种分布在南美洲西部从厄瓜多尔南部到智利中部。大多数大陆物种局限在距离海岸几公里的阿塔卡马沙漠，因此占据了近5000公里长的线性栖息地。这种分布在陆地脊椎动物中绝对是独一无二的。这项研究的主要目标将是使用来自七个不同基因区域的DNA序列和计算机辅助的树构建算法来重建这一组中所有物种的进化关系，以测试树中确定的特定系谱组的支持强度。该项目具有广泛的重要意义，原因有两个。首先，早期的研究表明，这一组大陆物种的祖先曾两次独立殖民加拉帕戈斯群岛，但这些研究都没有基于对所有大陆物种的抽样，因此可以解释为不完全抽样的结果可能是虚假的。贝纳维德斯现在已经收集了所有公认的大陆物种，并可以通过更强大的统计分析来克服这种批评，这是早期研究人员无法获得的。第二，加拉帕戈斯群岛内岛屿的殖民顺序至少有三种备选方案，但由于抽样限制，无法对备选方案进行严格评估。Sites和Benavides已经获得了加拉帕戈斯群岛的所有分类群，只剩下两个，并将在本研究期间收集丢失的物种；这种更完整的抽样设计加上广泛的分子数据，将根据统计上可靠的假设，为加拉帕戈斯独特的动物群的组装和进化提供更清晰的图景。

A grant has been awarded from the National Science Foundation to Dr. Jack Sites and Mr. Edgar Benavides, Brigham Young University, to study the "Phylogeny of the South American lizard genus Microlophus." This genus consists of 22 recognized species with an extremely unusual geographic distribution; 9 species are found only in the Galapagos islands, ~ 1000 km off the west coast of Ecuador in the eastern Pacific, while the remaining 13 species occur in western South America from southern Ecuador to central Chile. Most of the mainland species are confined to the Atacama Desert within a few km of the coast, and thus occupy a linear 'strip' of habitat almost 5000 km long. This distribution is absolutely unique among land vertebrates. The main objective of the study will be to reconstruct the evolutionary relationships of all species in this group using DNA sequences from seven different gene regions, and computer-assisted tree-building algorithms to test the strength of support for specific genealogical groups identified in the trees. The project is broadly significant for two reasons. First, earlier studies have suggested that ancestors of the mainland species of this group have colonized the Galapagos independently on two occasions, but none of these studies have been based on sampling of all mainland species, so results can be explained as possibly spurious consequences of incomplete sampling. Benavides has now collected all recognized mainland species, and can overcome this criticism with more statistically powerful analyses that were not available to earlier investigators. Second, there are at least three alternative scenarios for the sequence of coloniazation of islands within the Galapagos Archipelago, but again sampling limitations have not permit a rigorous evaluation of alternatives. Sites and Benavides have obtained all but two of the Galapagos taxa, and will collect the missing species during this study; this more complete sampling design coupled with extensive molecular data will give a clearer picture, based on statistically robust hypotheses, for the assembly and evolution of the unique Galapagos fauna.