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
Variation among 18 killifishes for phosphoglucomutase
Alleles
Patterns of Geographic Variation
• 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.
Example of subspeciesRecognizable subspecies would have to be allopatric.
Colaptes auratus caferColaptes auratus auratus
One problem: discordant character variation
Parapatric distributions withintergradation at boundaries
• 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.
“Racial” characters arequantitative characterscontinuous characterse.g. skin color
Phenotypic expressionin and among populationsgenerally fits a normal distribution
A common “racial” characteristic is skin color.
These groups easy to identify because of non-overlapping variation.
Gaps
685 nm
Skin color in 22 human populationsSamples of malesMean +/- one standard deviation
Clinal variation
• 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