Non-Allopatric Speciation in Animals

Futuyma, D. J., and G. C. Mayer (Department of Ecology and Evolution, State University of New York, Stony Brook, New York 11794 and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138) 1980. Non-allopatric speciation in animals. Syst. Zool., 29:254-271.-Major recent challenges to the view that animal speciation is usually allopatric are reviewed, and are found unconvincing, either because of their theoretical implausibility or because of insufficient evidence. Special attention is given to the theory of stasipatric speciation, and to purported cases, especially in tephritid fruit flies, of sympatric speciation associated with a shift to a new host. Stasipatric speciation is unlikely under population genetic theory; moreover, chromosome rearrangements probably seldom facilitate speciation. In the tephritid genus Rhagoletis, the archetypal case of sympatric speciation, there is little or no evidence of genetic divergence or of sympatric speciation. The conditions under which host-associated sympatric speciation might occur are so exacting as to be met by very few species. [Rhagoletis; Didymuria; Vandiemenella; Mus; Sceloporus; speciation; sympatric speciation; parapatric speciation; allopatric speciation; chromosome races; isolating mechanisms; host selection.] “It is in the nature of science that once a position becomes orthodox it should be subjected to criticism …. It does not follow that, because a position is orthodox, it is wrong …. -Maynard Smith, 1976 Until recently, it has been widely accepted that speciation in animals usually proceeds by the differentiation of geographically isolated populations (e.g., Dobzhansky, 1970; Lewontin, 1974; Rosenzweig, 1975; Dobzhansky et al., 1977). The reasons for this belief were developed in extenso by Mayr (1942, 1963, 1970), who argued that other modes of speciation were so unlikely as to be insignificant. Since 1963, there have been several important challenges to this view (e.g., Maynard Smith, 1966; Bush, 1975a; White, 1978a). Because White’s (1978a) book, devoted largely to demonstrating the prevalence of non-allopatric speciation, seems likely to have an important impact on the climate of opinion on this topic, it is useful at this time to review the extent to which the theory and evidence amassed since 1963 warrant a major change in our views of animal spe-