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Phenotypic variation in the GAB character A. sexlineata : reproduces sexually

Phenotypic variation in the GAB character A. sexlineata : reproduces sexually Recombination of homologous chromosomes A. tesselata : reproduces parthenogenetically Recombination of sister chromosomes Therefore, source of variation in GAB is not recombination. Conchas: GPI variation

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Phenotypic variation in the GAB character A. sexlineata : reproduces sexually

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  1. Phenotypic variation in the GAB character A. sexlineata: reproduces sexually Recombination of homologous chromosomes A. tesselata: reproduces parthenogenetically Recombination of sister chromosomes Therefore, source of variation in GAB is not recombination. Conchas: GPI variation GPI ac: low counts ancestral GPI ab: high counts

  2. Variation among 18 killifishes for phosphoglucomutase Alleles

  3. Patterns of Geographic Variation

  4. Arrangement of phenotypic variation in natural populations • Some populations recognized as subspecies • A biological race = a subspecies. • Phenotypically diagnosable populations occupying allopatric subdivisions of the range of a species. • Subspecies have accumulated different allelic variation (via mutation). • Therefore, they express different fixed characteristics.

  5. Example of subspecies Recognizable subspecies would have to be allopatric. Colaptes auratus auratus Colaptes auratus cafer

  6. One problem: discordant character variation Parapatric distributions with intergradation at boundaries

  7. Second problem: subspecies may be nothing more than slices of clinal variation • Cline = a character gradient • E.g. human race concept. • There is no satisfactory biological definition of a human race! • Misconception: there are character states unique to particular groups of humans • The characters traditionally used are quantitative characters with continuous variation.

  8. “Racial” characters are quantitative characters continuous characters e.g. skin color Phenotypic expression in and among populations generally fits a normal distribution

  9. A common “racial” characteristic is skin color.

  10. These groups easy to identify because of non-overlapping variation. Gaps 685 nm

  11. Clinal variation Skin color in 22 human populations Samples of males Mean +/- one standard deviation

  12. There IS geographic structuring of allele frequencies. • Genetic distance map • 42 native human populations • Distances based on frequencies of 120 different alleles • Closer proximity in graph = greater genetic similarity • Genetic similarity is related to geographic distances among the groups. • PPPPPopu Population differences

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