Interbreeding of Natural Populations of Vertebrates

Abstract

Literature pertinent to the hybridization of vertebrate spp. and subspp. is reviewed. Closely related spp. of vertebrates are frequently interfertile, and interbreeding of sympatric spp. is prevented by complexes of isolating mechanisms. Hybrids between sympatric spp. of vertebrates are rare, and they usually occur where there has been a breakdown of ecological isolation. Geogr. races are originated and perpetuated through mutations, selection, and restrictions on gene flow. An equilibrium between gene flow and selective elimination of immigrants must exist to permit the origin and continued existence of geographic races. Stages of speciation of some Pleistocene-fragmented, vertebrate populations in N. America are discussed in respect to their possible interbreeding.