Page 12 - Research 1.0

each such sub population will carry a subset of the parent
population genome, but subsequent mutations will be unique to
each new population (the genotype) that will come to
differentiate that population from others (Genetic Drift).

To the extent that such populations encounter differing
environmental conditions, that environment will exert
different evolutionary pressures on that population. New
mutations will have a much greater chance of coming to
dominance within a smaller population than they would in the
larger parent population where they would be one among the

many. Over thousands of generations genetic differences
accumulate in the different gene pools making interbreeding
ever more difficult until at some point speciation can be
said to have occurred. Because speciation is a process, rather
than an event, it would be no more possible to pinpoint where
speciation occurred than to identify where on the color
spectrum orange becomes red.

http://i.imgur.com/xWpvw.jpg

https://evolution.berkeley.edu/evolibrary/article/evo_01