Vicariance Biogeography:
Idea that present day distributions are due to disruption of a once widespread range
1. Ancestral species is widespread over an area.
2. Some geologic event (e.g. mountain building, continental drift, etc.) leads to separation of ancestral populations.
3. Allopatric speciation leads to formation of new species.
BARRIER IS YOUNGER THAN ANCESTRAL SPECIES.
Incorporates geology into explanation of distributions