Evolution Thru Mt 2-Population Genetics: Migration

Front 1

adding migration to HWE

Back 1

•homogenizing evolutionary force across populations; therefore often preventing divergence of populations
•FST- 0 (no population differentiation) to 1 (great genetic differentiation between pops)

Front 2

Water snakes of Lake Erie -example of migration effects

Back 2

-migration and natural selection working against each other
-have two different color morphs of same species
-have mostly banded snakes on islands
-mostly unbanded on islands
-migration tends to move from mainland to islands
-islands have selective force favoring unbanded morphs

Front 3

selection and mutation effects on HWE

Back 3

-selection can push traits one way or the other-directional and often reduces genetic diversity-shifts curve, and makes it smaller
-MHC [? histamine complex] selection an example of selection that increases diversity
-selection probably causes more differentiation between isolated populations than homogenization but it depends on the selective pressure
-mutation increases genetic diversity but start at very low levels-causes isolated populations to differentiate

Front 4

Models of Gene Flow

Back 4

1. Island model
2. Stepping-stone model
3. Isolation by distance model

Front 5

Island model

Back 5

multiple populations connected with each other , individuals from one population move to other populations -might see in a more homogeneous area with no major barriers

Front 6

Stepping stone model

Back 6

-have to go thru populations sequentially (must go thru one to get to another) -might see in a chain of islands

Front 7

Isolation by distance model

Back 7

- (independent variable on x axis-distance, dependent variable on y-axis-genetic distance), would expect a positive linear relationship between genetic distance and geographic distance if population fits this model

Front 8

Estimates of Gene Flow:

Back 8

1. Direct estimates
2. Indirect estimates

Front 9

Direct estimates

Back 9

-trying to follow individuals and see if they contribute genetic material to next generation-difficult to collect-methods like radiotelemetry, satellite transmitters, GIS-can overlay movements on topography-don’t give much info about reproduction

Front 10

Indirect estimates

Back 10

-assignment test, evidence of gene flow thru the alleles