Emergent speciation by multiple 1 Dobzhansky – Muller incompatibilities

The Dobzhansky–Muller model posits that incompatibilities between alleles at different loci 5 cause speciation. However, it is known that if the alleles involved in a Dobzhansky–Muller 6 incompatibility (DMI) between two loci are neutral, the resulting reproductive isolation cannot 7 be maintained in the presence of either mutation or gene flow. Here we propose that speciation 8 can emerge through the collective effects of multiple neutral DMIs that cannot, individually, 9 cause speciation—a mechanism we call emergent speciation. We investigate emergent speciation 10 using a haploid neutral network model with recombination. We find that certain combinations 11 of multiple neutral DMIs can lead to speciation. Complex DMIs and high recombination rate 12 between the DMI loci facilitate emergent speciation. These conditions are likely to occur in 13 nature. We conclude that the interaction between DMIs may be a root cause of the origin of 14 species. 15