Phenotypic variation in the GAB character A. sexlineata: reproduces sexually Recombination of...
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Transcript of Phenotypic variation in the GAB character A. sexlineata: reproduces sexually Recombination of...
![Page 1: Phenotypic variation in the GAB character A. sexlineata: reproduces sexually Recombination of homologous chromosomes A. tesselata: reproduces parthenogenetically.](https://reader031.fdocuments.us/reader031/viewer/2022032310/56649d5e5503460f94a3e70f/html5/thumbnails/1.jpg)
Phenotypic variation in the GAB character
A. sexlineata: reproduces sexuallyRecombination of homologous chromosomes
A. tesselata: reproduces parthenogeneticallyRecombination of sister chromosomes
Therefore, source of variation in GAB is notrecombination.
Conchas: GPI variationGPI ac: low countsancestral
GPI ab: high counts
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Variation among 18 killifishes for phosphoglucomutase
Alleles
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Patterns of Geographic Variation
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• 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.
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Example of subspeciesRecognizable subspecies would have to be allopatric.
Colaptes auratus caferColaptes auratus auratus
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One problem: discordant character variation
Parapatric distributions withintergradation at boundaries
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• 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.
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“Racial” characters arequantitative characterscontinuous characterse.g. skin color
Phenotypic expressionin and among populationsgenerally fits a normal distribution
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A common “racial” characteristic is skin color.
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These groups easy to identify because of non-overlapping variation.
Gaps
685 nm
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Skin color in 22 human populationsSamples of malesMean +/- one standard deviation
Clinal variation
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• 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 Populationdifferences