How are new species formed?
Stage 2: Becoming Different.
Now that 2 or more populations are separate, they may be in slightly
different environments. Over many generations, they become adapted to these
environments under the influence of natural selection. The result is that the
different populations gradually become different.
Even in a small area, there may be differences in the environment,
and the 2 populations become adapted to differences in altitude or depth (in
water), sunny vs. shady places, different temperatures or amounts of rainfall,
or different soil types. All of these can limit several populations of the same
species from intermixing their genes and thus prevent them from staying the
same.
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Long & Slichter