key concept 22.2 Speciation Is a Natural Consequence of Population Subdivision

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Not all evolutionary changes result in new species. A single lineage may change over time without giving rise to a new species. Speciation requires the interruption of gene flow within a species whose members formerly exchanged genes. But if a genetic change prevents reproduction between individuals of a species, how can such a change spread through a species in the first place?

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  • The Dobzhansky–Muller model explains how reproductive isolation results from the accumulation of genetic incompatibilities following a splitting of the ancestral population (interruption of gene flow).

  • Greater genetic differences between species are correlated with increased reproductive isolation.