Natural Selection

Genetic Drift

Sexual Selection

Gene Flow

Genetic drift are random changes in a small population. The bottleneck and founder effect are examples. Also, small and poor sampling can be an example.

Genetic flow is the movement of alleles in and out of populations. ex. migration of an org to a new popn

homozygosity at a locus

allele frequencies fluctuate until the locus becomes monomorphic (AA or aa)

chance matings between individuals with similar genotypes

random differential reproductive success among individuals w/in a popn

Heterozygousity (H)

H= avg proportion of heterozygous loci per individual (must be neutral loci aka not selected on)

and avg Heterozygosity (Hbar)

Hbar=avg freq of heterozygotes across all loci genetic variation

What is the equation for H?

find H for two alleles that are equally likely at a loci

H = 1 - Σp_i²

where p_i = frequency of a given allele at a loci

so you add up the square of each allelic frequency at a loci.

so with two alleles that are equally likely to occur there will be an H of:

H=1-[(.5)²+(.5)²]=.5

inbreeding

Effective population size

proportion of the population that actually reporduces, the number of mature reproductively active adults

popn with a larger T typically have a smaller proportion of breeding adults

Ne/N decreases with T

spring peeper frogs (T=2)

freshwater turtles (T=15)

what is the symbol for mutation rate? what is the avg mutation rate for something?

mu

10^-4   to 10^-9   per gamete per generation

How does mu and Ne effect Heterozygosity?

How do we plot this?

an increase in either Ne or mu will cause and increase in H

We plot this with 4Ne(mu) on the x-axis and Heterozygosity (H) on the Y axis

First of all this will be an example range retraction causing RGD

these lizards used to be widespread through desert habitats.

then there was a climate change from aried to mesic

now the "relict" popn live in fragmented desert and these popn show RGD of their neutral alleles