A THEORETICAL ASSESSMENT OF RECOMBINATIONAL SPECIATION

Using a computer simulation, we have examined the dynamics of recombin ational speciation, a potentially rapid mode of evolution dependent on chromosomal reassortment in populations of partially sterile interspe cific hybrids. We describe how various parameters affect the time requ ired for a new recombinant species to become established within the se tting of a spatially structured hybrid zone. Our results indicate that recombinational speciation is most likely to occur where (1) the hybr id zone interface is long, (2) the organisms involved are predominantl y selfing, (3) the hybrids are relatively fertile, and (4) the number of differences in chromosomal structure between the parental species i s small. The speciation dynamics are characterized by long-term stasis followed by an abrupt transition to a new reproductively isolated typ e. The results are largely the same whether the nascent recombinant sp ecies is favoured by a fertility or a viability advantage. Recombinati onal speciation, like polyploidy, appears to be a feasible mechanism f or sympatric speciation in plants.