Cluster analyses using the amino acid content predicted from the coding regions (13 genes) of complete vertebrate mitochondrial genomes as traits grouped selected vertebrates into two clusters, terrestrial and aquatic...Cluster analyses using the amino acid content predicted from the coding regions (13 genes) of complete vertebrate mitochondrial genomes as traits grouped selected vertebrates into two clusters, terrestrial and aquatic vertebrates. Exceptions were the hagfish (Eptatretus burgeri), thought to be an early ancestor of vertebrates, and the black spotted frog (Rana nigromaculata), which is terrestrial as an adult and aquatic as a larva. These two species fall into the terrestrial and aquatic clusters, respectively. Using the nucleotide (G, C, T and A) content in the coding and non-coding regions, and in the complete genome as traits, similar results were obtained but with some additional exceptions. In addition, phylogenetic analyses of 16S rRNA sequences produced a consistent result. The results of this study indicated that vertebrate evolution is controlled by natural selection under both an internal bias as a result of nucleotide replacement genomic rules, and an external bias caused by environmental biospheric conditions.展开更多
It has become clear that the extant vertebrates are divided into three major groups, that is, hagfishes, lampreys, and jawed vertebrates. Morphological and molecular studies, however, have resulted in conflicting view...It has become clear that the extant vertebrates are divided into three major groups, that is, hagfishes, lampreys, and jawed vertebrates. Morphological and molecular studies, however, have resulted in conflicting views with regard to their interrelationships. To clarify the phylogenetic relationships between them, 48 orthologous protein-coding gene families were analyzed. Even as the analysis of 34 nuclear gene families supported the monophyly of cyclostomes, the analysis of 14 mitochondrial gene families suggested a closer relationship between lampreys and gnathostomes compared to hagfishes. Lampreys were sister group of gnathostomes. The results of this study supported the cyclostomes. Choice of outgroup, tree-making methods, and software may affect the phylogenetic prediction, which may have caused much debate over the subject. Development of new methods for tackling such problems is still necessary.展开更多
文摘Cluster analyses using the amino acid content predicted from the coding regions (13 genes) of complete vertebrate mitochondrial genomes as traits grouped selected vertebrates into two clusters, terrestrial and aquatic vertebrates. Exceptions were the hagfish (Eptatretus burgeri), thought to be an early ancestor of vertebrates, and the black spotted frog (Rana nigromaculata), which is terrestrial as an adult and aquatic as a larva. These two species fall into the terrestrial and aquatic clusters, respectively. Using the nucleotide (G, C, T and A) content in the coding and non-coding regions, and in the complete genome as traits, similar results were obtained but with some additional exceptions. In addition, phylogenetic analyses of 16S rRNA sequences produced a consistent result. The results of this study indicated that vertebrate evolution is controlled by natural selection under both an internal bias as a result of nucleotide replacement genomic rules, and an external bias caused by environmental biospheric conditions.
基金the National Natural Science Foundation of China （No. 60575005） the Natural Science Foundation of Liaoning Province （No. 20072152）+3 种基金 Key Project of Science and Technology of the Educational Ministry of China （No. 206032） the Science and Technology Project of Dalian City （No. 2006E11SF068） the National High Technology Research and Development Program of China （No. 2007AA09ZA28） the National Basic Research Program of China （No. 2007CB815802）.
文摘It has become clear that the extant vertebrates are divided into three major groups, that is, hagfishes, lampreys, and jawed vertebrates. Morphological and molecular studies, however, have resulted in conflicting views with regard to their interrelationships. To clarify the phylogenetic relationships between them, 48 orthologous protein-coding gene families were analyzed. Even as the analysis of 34 nuclear gene families supported the monophyly of cyclostomes, the analysis of 14 mitochondrial gene families suggested a closer relationship between lampreys and gnathostomes compared to hagfishes. Lampreys were sister group of gnathostomes. The results of this study supported the cyclostomes. Choice of outgroup, tree-making methods, and software may affect the phylogenetic prediction, which may have caused much debate over the subject. Development of new methods for tackling such problems is still necessary.
