REU: Molecular Phylogeny for Select Tetrapods

经典的系统发育树，描绘了现存的四足动物群体、鸟类和鳄鱼之间的关系，它们是彼此最接近的亲缘关系。我们实验室最近的分子研究和对其他一些形态和分子数据的分析表明，鸟类与哺乳动物的亲缘关系可能比与鳄鱼的亲缘关系更近。进化缓慢的18S和28S核糖体RNA(RRNA)基因是研究包括四足动物在内的现存物种之间进化关系的优秀探针。从其他种类的羊膜动物中收集rRNA序列数据将允许对相关关系的替代假设进行测试。活着的两栖动物被分成三类：青蛙、火蜥蜴和鱼纲动物。毛虫是一种无肢动物，在世界各地的热带地区都能找到。将从尾虫中收集28S核rRNA基因和两个线粒体基因(12S rRNA和细胞色素b)的核苷酸序列数据，以检查该种群内的进化关系。尾虫是研究生物地理学的理想生物，因此了解它们之间的关系将特别重要，这是了解过去分布所必需的。

The classical phylogenetic tree depicting relationships among living tetrapods groups birds and crocodilians as each others closest genetic relatives. Recent molecular studies in our laboratory and some analyses of morphological and molecular data of others has suggested that birds may be more closely related to mammals than to crocodilians. The slow-evolving 18S and 28S nuclear ribosomal RNa (rRNA) genes are excellent probes for examining evolutionary relationships among living species, including the tetrapods. Collecting rRNA sequence data from additional species of amniotes will permit alternative hypotheses of relationships to be tested. The living amphibians are placed in three groups: frogs, salamanders, and caecilians. The caecilians are limbless animals which are found in tropical areas throughout the world. Nucleotide sequence data from the 28S nuclear rRNA gene and two mitochondrial genes (12S rRNA and cytochrome b) will be gathered from caecilians in order to examine evolutionary relationships within this group. Caecilians are ideal organisms for study biogeography and therefore knowledge of their relationships, needed for understanding past distributions, will be especially important.