Molecular phylogenetics and evolution of batoid fishes /
Mitochondrial DNA sequences from 19 species of batoid fishes and four outgroup taxa were analyzed phylogenetically. DNA sequences included the complete 12S rRNA gene, seven tRNA genes, and fragments of four protein coding genes. Investigations focused on relationships of major batoid lineages. Th...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728908121&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Mitochondrial DNA sequences from 19 species of batoid fishes and four outgroup taxa were analyzed phylogenetically. DNA sequences included the complete 12S rRNA gene, seven tRNA genes, and fragments of four protein coding genes. Investigations focused on relationships of major batoid lineages. The results were sensitive to method of analysis; maximum parsimony analyses were outgroup-dependent, whereas, maximum likelihood was insensitive to outgroup sampling. The maximum likelihood topology suggested two novel relationships. First, Pristiformes, Rhinobatidae and Platyrhinidae formed a clade, which was at the base of the topology. Second, Rajidae was placed sister to Torpediniformes. The same DNA sequences also were used to compare rates of evolution in batoids and sharks. Sharks have a slower rate of evolution relative to mammals, often attributed to the slower metabolic rate of sharks (metabolic rate hypothesis). This study suggests that batoids, despite having slower metabolic rates, have a rate of molecular evolution that is three times faster than sharks. This pattern contradicts the metabolic rate hypothesis, and suggests that other factors must be responsible for differences in molecular rates between sharks and mammals. Mitochondrial DNA from ten species of myliobatoids and four outgroup taxa also were analyzed phylogenetically. Sequences included the complete 12S rRNA gene, four tRNA genes, and three protein coding genes, for which sequences of one gene (cytochrome b) were obtained from GenBank. Cytochrome b was not available for four taxa, resulting in a large number of characters with missing data. A simulation study, undertaken to examine effects of missing data on phylogenetic analysis of myliobatoids, indicated that the two methods were affected differently by missing data. Maximum parsimony suffered from a large reduction in accuracy when characters with missing data were included. Maximum likelihood, however, did not suffer any reduction in accuracy when missing data were included. Maximum likelihood analyses of the real data were largely consistent with morphology based hypotheses; however, two novel relationships were obtained. Urobatis was placed sister to Himantura and Potamotrygon, and Dasyatis was placed within a clade of benthic stingrays. The molecular data agreed with morphological studies in placing Himantura sister to freshwater stingrays. |
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| Item Description: | Vita. "Major Subject: Wildlife and Fisheries Sciences". |
| Physical Description: | xi, 115 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 100-114). |