Lecture 20 population structure, gene flow and genetic drift Flashcards
What is migration?
the movement of individuals from one population to another
What is a population?
a group of individuals of the same species occupying a given area at the same time
What is gene flow?
any mechanism that allows genes to flow from one population to another
What are Key questions for evolutionary studies of variation within populations? (2)
How many of these variations are genetic in origin?
Does variation contribute to fitness differences among organisms?
What are Key questions for geographical differentiation? (2)
What proportion of genetic variation in a species is found within a population vs between populations?
How is diversity distributed within and between populations?
Are the differences between populations heritable and adaptable?
What is the job of gene flow?
to homogenize
How does drift affect populations?
causes populations to be different
What are ways to measure gene flow?
Experiments
Neutral genetic markers
Polymorphic genetic variants that are not direct targets of selection
If two populations have different genes, one fully F and only fully G what gene will the offspring have?
FG gene
If there is a field of crop and weed sunflowers, what happens to gene flow the further these are from each other?
Less gene flow
What is genetic drift?
Random fluctuations in alleles
Does genetic drift lead to particular direction of evolutionary change?
No
What are stochastic evolutionary forces? MRG
Mutations
Recombination
Genetic drift
What is a deterministic evolutionary force?
Natural selection
What are Stochastic changes in allele frequency due to?
random variation in fecundity and mortality
What type of population size do stochastic changes affect?
Small populations
What is Population bottlenecks?
A single sharp reduction in abundance followed by a rebound
How does Population bottlenecks affect biodiversity?
Results in loss of biodiversity
What is the Founder effect?
When a few individuals from a population colonize a new area
What is the diversity like in the colonizing group compared to the source group?
colonizing group contains only limited diversity compared to the source group
Which type of population size is genetic drift more common in?
Genetic drift more prominent in small populations
What are the effects of genetic drift? (4) FDAC
More drastic fluctuations each generation
Rapid loss of genetic diversity
Faster allele fixation of loss
Less consistency across replicate populations
what factors make a phenotype?
genomic and environmental factors
do genotypes grow the same in every environment?
no
what is phenotypic plasticity?
ability of a genotype to modify its phenotype in response to environmental changes
what organism is phenotypic plasticity most common in?
plants and corals
do all phenotypic plasticity result from adaptation
no
what is done in reciprocal transplant studies?
Growing gene types in different environments and comparing the phenotypes in different environments
Reciprocal transplant studies provide evidence of?
local adaptation
what do reciprocal transplants enable?
Enables measurement of selection against non-local genotypes
what components does Reciprocal Transplant Studies separate phenotypic variation into?
genetic and environmental components
what were the conclusions in the Clausen-Keck-Hiesey Transplant?
Differences between populations are due to BOTH plasticity and genetics
Evidence from widespread local adaptation because local populations had the highest fitness
what does high UV radiation select for in terms of skin pigmentation? what does it interfere with?
May select for increased pigmentation
Interferes with folate (the natural form of vitamin B9, water-soluble and naturally found in many foods)
what does low UV radiation select for in terms of skin pigmentation? what does it reduce the making of?
Reduced making of vitamin D
Increase selection for reduced pigmentation
is there a single best phenotype across the globe? why
No single best phenotype across the globe due to tradeoffs
what was the history of Local adaptation on skin pigmentation?(4) NADl
Numerous genes are known to affect skin pigmentation.
Alleles of these genes show rapid allele frequency change over time using ancient genomes (indicates natural selection).
Alleles of these genes show higher between population differentiation than most other genes.
Evidence supporting a history of local adaptation
