Speciation: Sympatric and Parapatric

Abstract Sympatric and parapatric speciation refer to the origin of species in the absence of complete geographic isolation between the diverging taxa. Until recently, most biologists believed that geographic isolation was an obligatory stage in the development of most species, i.e. most species originated in allopatry. However, new empirical and theoretical studies have shown that speciation may occur despite the incipient species having adjacent or overlapping geographic ranges.