Speciation via habitat specialization: the evolution of reproductive isolation as a correlated character

Summary A diverse group of theoretical and empirical studies are integrated into a composite model of sympatric speciation via habitat specialization. It is shown that disruptive selection on a continuous distribution of habitat preference can lead to the evolution of prezygotic reproductive isolation as a correlated character. The form of selection eliminates the major theoretical objections to the process of sympatric speciation. The principal difference between this model and the allopatric model of speciation is that the initial barrier to gene flow between subpopulations is produced by the evolution of gaps in the phenotypic distribution of spatial/temporal habitat use, rather than an extrinsic geographical barrier.