What is the correct order of the stages of speciation?

First Stage: Separation

Speciation usually begins when a part of a population becomes separated from the rest of their species.

Second Stage: Adaptation

Adaptation in speciation is quite similar, though the groups may evolve different sets of traits if the environmental conditions differ for each group.

Third Stage: Reproductive Isolation

Reproductive isolation is when groups of a same species are reunited and cannot interbreed with each other anymore, so they are now identified as different species.

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