Open AccessGenomic Evidence for Speciation with Gene Flow in Broadcast Spawning Marine Invertebrates
Author(s) -
Shotaro Hirase,
Yo Y. Yamasaki,
Masashi Sekino,
Masato Nishisako,
Mitsuru Ikeda,
Motoaki Hara,
Juha Merilä,
Kiyoshi Kikuchi
Publication year - 2021
Publication title -
molecular biology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.637
H-Index - 218
eISSN - 1537-1719
pISSN - 0737-4038
DOI - 10.1093/molbev/msab194
Subject(s) - biology , gene flow , gigantea , allopatric speciation , sympatry , reproductive isolation , sympatric speciation , population , ecology , evolutionary biology , genetic algorithm , marine invertebrates , disruptive selection , natural selection , genetic variation , genetics , gene , botany , demography , sociology
How early stages of speciation in free-spawning marine invertebrates proceed is poorly understood. The Western Pacific abalones, Haliotis discus, H. madaka, and H. gigantea, occur in sympatry with shared breeding season and are capable of producing viable F1 hybrids in spite of being ecologically differentiated. Population genomic analyses revealed that although the three species are genetically distinct, there is evidence for historical and ongoing gene flow among these species. Evidence from demographic modeling suggests that reproductive isolation among the three species started to build in allopatry and has proceeded with gene flow, possibly driven by ecological selection. We identified 27 differentiation islands between the closely related H. discus and H. madaka characterized by high FST and dA, but not high dXY values, as well as high genetic diversity in one H. madaka population. These genomic signatures suggest differentiation driven by recent ecological divergent selection in presence of gene flow outside of the genomic islands of differentiation. The differentiation islands showed low polymorphism in H. gigantea, and both high FST, dXY, and dA values between H. discus and H. gigantea, as well as between H. madaka and H. gigantea. Collectively, the Western Pacific abalones appear to occupy the early stages speciation continuum, and the differentiation islands associated with ecological divergence among the abalones do not appear to have acted as barrier loci to gene flow in the younger divergences but appear to do so in older divergences.