Parapatric Speciation - Environmental Gradients

Environmental Gradients

Because of the continuous nature of parapatric population distribution, population niches will often overlap and produce a continuum in the species’ ecological role across an environmental gradient. Whereas in allopatric or peripatric speciation - in which geographically isolated subpopulations may produce discretely separate niches - the reduced gene flow of parapatric speciation will often produce a cline in which a variation in evolutionary pressures causes a change to occur in allele frequencies within the gene pool between populations. This environmental gradient ultimately results in genetically distinct sister species.