BIOL 131 Isolation and divergence in Allopatry Summary

24.2 Isolation and divergence in Allopatry
Ð Populations that are geographically separated are
said to be in allopatry (Òdifferent-homeland"). Thus,
speciation that begins with geographic isolation is
known as allopatric speciation.

Ð Allopatric speciation starts in one of two ways: (1)
dispersal,the movement of individuals from one
place to another, or (2) vicariance, the physical
splitting of a habitat.
Ð As the general model in Figure 24.5a illustrates, a
population can disperse to a new habitat, colonize
it, and found a new population.

Ð Alternatively, a new geographic barrier can split a
population
into two or more subgroups that are physically isolated
from each other (Figure 24.5b). These processes take us
into the field of biogeography- the study of how species
and populations are
distributed geographically

Allopatric speciation by dispersal
Ð Could this dispersal event lead to speciation? To
evaluate this question, the Grants caught, weighed,
and measured most of the parents and offspring
produced on Daphne Major over the succeeding 12
years. When they compared these data with
measurements of large ground finches in the
migrant population, they discovered that the