Migration (Lecture 11) Flashcards
Fixation
An allele goes to 100%
Mainland/Island Model
Simplest model (Pc to Pi); continent to island
Stepping Stone
Multiple populations; migration between geographically adjacent populations
Stepping Stone one dimension model
Riverrine model (spot to spot)
Stepping Stone 2-Dimension
Patchy grassland; migrating between multiple places; not specific intermediate stops
Isolation by distance
Migration between places but not only adjacent habitats
Isolation by distance rates
Rates become lower as distance gets larger
Mechanisms of gene flow
Any movement of any part of an organism that carry the genes and reproduce in the new environment; depends on organisms life history/biology
Example of mechanisms of gene flow
Pollen, adults, juveniles etc.
Populations size does not impact the
Number of migrants per generation will prevent differences in populations; all you need is 1 because you need someone to settle drift so that fixation doesn’t occur
Homogenization
Makes populations more similar
m=
Migration rates
Mu=
mutation
C=
Continent/mainland
0=m(-Pi+Pc)
Equilibrium
There are no allele frequency changes when
m=0; no migration; when -Pi=Pc, when island frequency= the continent frequency
Migration reduces
Differentiation among populations
When migration counteracts natural selection,
An intermediate equilibrium is reached between the two processes
Cline
Geographic regions of change in some trait; relatively smooth transition across space
Example of Cline graphs
More migration makes a shallower line; Change in Cline slope over time, no differential selection with migration will produce a flat line
Ecology and behavior can have profound impacts on
Gene flow and thus evolutionary dynamics
Disruption of gene flow is usually a requirement for
speciation
