1 Tetraploidy and the Evolution of Salmonid Fishes.- 1. Introduction: Polyploidy in Vertebrate Evolution.- 2. The Salmonid Tetraploid Event.- 2.1. Evidence for Ancestral Polyploidy.- 2.2. Time of the Event.- 2.3. Nature of the Tetraploid Event.- 3. Evolution of Chromosomes.- 3.1. Ancestral and Extant Karyotypes.- 3.2. Evolution of Disomy.- 4. Evolution of Proteins.- 4.1. Possible Fate of Protein Loci.- 4.2. Salmonid Enzymes.- 4.3. Regulation of Enzyme Loci.- 5. The Current Salmonid Genetic System.- 5.1. Sex Chromosomes and Sex Determination.- 5.2. Genetic Recombination.- 5.3. Aneuploidy and Polyploidy.- 5.4. Patterns of Genic Inheritance.- 5.5. Implications of Nondisomic Inheritance.- 6. Adaptive Significance of Polyploidy in Salmonids.- 6.1. Short-Term Success.- 6.2. Long-Term Success.- 7. Summary.- References.- 2 Tetraploidy and the Evolution of the Catostomid Fishes.- 1. Introduction.- 1.1. The Role of Gene Duplication in Evolution.- 1.2. Origin of the Catostomidae.- 1.3. Disomic versus Tetrasomic Inheritance.- 1.4. Early Biochemical Studies.- 2. Experimental and Theoretical Approaches.- 2.1. Starch Gel Electrophoresis and Activity Staining.- 2.2. Determination of the Number of Functional Gene Copies.- 2.3. Determination of Locus Homologies.- 3. Pathways of Duplicate Gene Evolution.- 3.1. Gene Silencing.- 3.2. Molecular Basis of Gene Silencing.- 3.2. Structural Divergence of Proteins.- 3.4. Evolution of the Regulation of Duplicate Genes.- 4. Population Genetics.- 4.1. Genetic Variability.- 4.2. Mathematical Models of the Rate of Gene Silencing.- 5. Systematics.- 5.1. Gene Duplication Analyses and Allozyme Approaches.- 5.2. Species Hybridization.- 6. Speculations on Catostomid Evolution and Directions for Future Research.- 6.1. The Advantages of Polyploidy.- 6.2. Future Research.- References.- 3 A New Look at Sex Determination in Poeciliid Fishes.- 1. Introduction.- 2. Polygenic Sex Determination in Fishes.- 3. The H-Y Locus.- 4. Polygenic Sex Determination in Mammals.- 5. The Sex-Determining Mechanism of the Platyfish, Xiphophorus maculatus.- 6. The Sex Ratio in the Swordtail, Xiphophorus helleri.- 7. Do Swordtails Change Sex?.- 8. Taxonomy and the Induction of the Heterogametic Gonad by H-Y (H-W).- 9. Atypical Sex Determination in Fishes.- 9.1. XX Males.- 9.2. WW, WX, and WY Males in the Platyfish.- 9.3. XY and YY Females in Xiphophorus maculatus.- 9.4. XY Females in Xiphophorus montezumae and Xiphophorus milleri.- 10. The Relationship between Atypical Sex Determination, Sex Ratio, Age at Maturity, and Adult Size.- 11. Most Small Males of Xiphorphorus nigrensis (Río Choy) Are XX.- 12. The Frequency of the Autosomal Factors for Atypical Sex Determination in Natural Populations of Xiphophorus.- 13. The Effect of Extrinsic Factors on Sex Determination in Fishes.- 14. Sex Ratios and Sex Determination in Species Hybrids.- 15. The Sex-Determining System of Xiphophorus helleri.- 16. Summary.- Appendix. Sex Ratio Data for Various Xiphophorus Stocks.- References.- 4 Gene Mapping in Fishes and Other Vertebrates.- 1. Introduction.- 1.1. Evolutionary Stability of Linkage Groups.- 1.2. A Perspective on Gene Mapping.- 1.3. Genetic Maps of Protein-Coding Loci in Vertebrates.- 2. Linkage Relationships of Protein-Coding Loci in Fishes.- 2.1. Xiphophorus, Poeciliidae.- 2.2. Homology of Xiphophorus Proteins with Those Studied in Other Fishes.- 2.3. Poeciliopsis, Poeciliidae.- 2.4. Poecilia reticulata, Poeciliidae.- 2.5. Freshwater Sunfishes, Centrarchidae.- 2.6. Trout and Salmon, Salmonidae.- 3. Comparisons of Linkage Groups of Fishes with Other Vertebrates.- 4. Potential for Expansion of Linkage Maps in Fishes.- 5. Uses of Linkage Maps.- References.- 5 The Evolutionary Genetics of Xiphophorus.- 1. Introduction.- 2. Materials and Methods.- 2.1. Allozyme Variation.- 2.2. Symbols, Calculations, and Statistics.- 2.3. Collecting Localities.- 3. Five Sets of Polymorphic Loci.- 3.1. The Tailspot Locus.- 3.2. Tailspot Pattern Modifiers.- 3.3. B
It is my hope that this collection of reviews can be profitably read by all who are interested in evolutionary biology. However, I would like to specifically target it for two disparate groups of biologists seldom men tioned in the same sentence, classical ichthyologists and molecular biologists. Since classical times, and perhaps even before, ichthyologists have stood in awe at the tremendous diversity of fishes. The bulk of effort in the field has always been directed toward understanding this diversity, i. e. , extracting from it a coherent picture of evolutionary processes and lineages. This effort has, in turn, always been overwhelmingly based upon morphological comparisons. The practical advantages of such compari sons, especially the ease with which morphological data can be had from preserved museum specimens, are manifold. But considered objectively (outside its context of "tradition"), morphological analysis alone is a poor tool for probing evolutionary processes or elucidating relationships. The concepts of "relationship" and of "evolution" are inherently genetic ones, and the genetic bases of morphological traits are seldom known in detail and frequently unknown entirely. Earlier in this century, several workers, notably Gordon, Kosswig, Schmidt, and, in his salad years, Carl Hubbs, pioneered the application of genetic techniques and modes of reasoning to ichthyology. While certain that most contemporary ichth yologists are familiar with this body of work, I am almost equally certain that few of them regard it as pertinent to their own efforts.
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