Lecture 6 -Phenotypic Evolution Flashcards
What does the selection gradient measure?
strength of directional selection on a quantitative trait
How does the selection gradient measure the strength of directional selection?
measures the trait of interest and the fitness for a set of individuals who vary in the trait of interest
When beta is positive, what does this say about the strength of directional selection?
directional selection favors larger values of the trait
When beta is negative, what does this say about the strength of directional selection?
selection favors smaller values of the trait
When beta is 0, what does this say about the strength of directional selection?
there is no directional selection acting
What values of selection gradient indicate a moderately strong directional selection?
-0.5 and 0.5
What value of selection gradient indicates a strong directional selection?
1
How can we predict the amt of evolutionary change given directional selection?
by calculating the difference btw mean of a trait at the start of generation and the mean of trait now
What does the Breeder’s equation predict?
amt of evolutionary change that results from selective breeding
What is breeders equation formula?
delta z = change in the mean of the trait
delta z = (mean of trait in present generation)- (mean of trait in next generation) = (selection differential)(heritability)^2
What does h^2=0 mean?
no resemblance between parents and offspring
What does it mean if h^2=1?
parents and offspring are identical
What does it mean if heritability shows a positive slope?
trait is heritable between parents and offspring
What happens when S=0?
no change in the mean of the trait and thus no evolutionary change
What does h^2 indicate?
heritability = slope of regression line of a mean value trait from two parents and the value of trait in their offspring
