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Allopatric Speciation: Dispersal and Vicariance

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Allopatric speciation occurs when geographic separation blocks gene flow, so populations diverge independently, whether by dispersal or by vicariance dividing a range.

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A new lake dividing one rodent population, or a seed dispersing to a distant island, both start allopatric speciation by blocking flow.

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Dispersal and vicariance both block gene flow, differing only in whether the population moved or the landscape divided.