Genomic Regulation Of Nascent Speciation

Speciation is a process involving the evolution of reproductive barriers that lead to isolated species.Previous studies on the mechanism of speciation have focused on the visible reproductive isolation between species or subspecies,that is,during the middle and late stages of speciation.But the reason for this weak reproductive isolation in nascent speciation is not clear.In this study,we used crossbreeding between European large white pig and East Asian min pig to explore the evolution of reproductive isolation and genetic structure during nascent speciation.Although the Haldane's rule is not evident in many crosses of Eurasian domestic pigs,our data suggest that weak reproductive isolation has evolved in domestic pigs,which provides an ideal model for studying the nascent speciation.We found that during nascent speciation in pigs,autosomal influences on hybrid inviability to survive and hybrid male inviability to survive were significant,but not so evident on the X chromosome.Our evidence in pigs confirms the unusual role of autosomes in the non-survival of hybrids in nascent speciation,and that the X chromosome plays an important role in mid to late speciation.Partial hybrid male inviability has successfully evolved from partial hybrid inviability by breaking the DMI effect symmetry between two sexes.The genomic incompatibility is enriched in pathways for angiogenesis,androgen receptor signaling and immunity.Taken together,we show that the Eurasian domestic pig can serve as an ideal model for studying early speciation,where weak Dobzhansky-Muller incompatibilities(DMIs)begin to evolve in a part of the Eurasian pig genome.Using pig models,the evolutionary rules of early speciation can be studied in depth,and the unique phenomena observed in domestic pigs may help to fill in the gaps in knowledge related to the evolution from moderately differentiated populations to reproductively isolated species.