A THEORETICAL ASSESSMENT OF RECOMBINATIONAL SPECIATION

Using a computer simulation, we have examined the dynamics of recombinational speciation, a potentially rapid mode of evolution dependent on chromosomal reassortment in populations of partially sterile interspecific hybrids. We describe how various parameters affect the time required for a new recombinant species to become established within the setting of a spatially structured hybrid zone. Our results indicate that recombinational speciation is most likely to occur where (1) the hybrid zone interface is long, (2) the organisms involved are predominantly selfing, (3) the hybrids are relatively fertile, and (4) the number of differences in chromosomal structure between the parental species is small. The speciation dynamics are characterized by long-term stasis followed by an abrupt transition to a new reproductively isolated type. The results are largely the same whether the nascent recombinant species is favoured by a fertility or a viability advantage. Recombinational speciation, like polyploidy, appears to be a feasible mechanism for sympatric speciation in plants.