Assortative mating and persistent reproductive isolation in hybrids. Author Molly Schumer, Daniel Powell, Pablo Delclós, Mattie Squire, Rongfeng Cui, Peter Andolfatto, Gil Rosenthal Publication Year 2017 Type Journal Article Abstract The emergence of new species is driven by the establishment of mechanisms that limit gene flow between populations. A major challenge is reconciling the theoretical and empirical importance of assortative mating in speciation with the ease with which it can fail. Swordtail fish have an evolutionary history of hybridization and fragile prezygotic isolating mechanisms. Hybridization between two swordtail species likely arose via pollution-mediated breakdown of assortative mating in the 1990s. Here we track unusual genetic patterns in one hybrid population over the past decade using whole-genome sequencing. Hybrids in this population formed separate genetic clusters by 2003, and maintained near-perfect isolation over 25 generations through strong ancestry-assortative mating. However, we also find that assortative mating was plastic, varying in strength over time and disappearing under manipulated conditions. In addition, a nearby population did not show evidence of assortative mating. Thus, our findings suggest that assortative mating may constitute an intermittent and unpredictable barrier to gene flow, but that variation in its strength can have a major effect on how hybrid populations evolve. Understanding how reproductive isolation varies across populations and through time is critical to understanding speciation and hybridization, as well as their dependence on disturbance. Keywords Animals, Biological Evolution, Gene Flow, Genetic Speciation, Reproductive Isolation, Genome, Cyprinodontiformes, Whole Genome Sequencing, Mating Preference, Animal Journal Proc Natl Acad Sci U S A Volume 114 Issue 41 Pages 10936-10941 Date Published 2017 Oct 10 ISSN Number 1091-6490 DOI 10.1073/pnas.1711238114 Alternate Journal Proc Natl Acad Sci U S A PMCID PMC5642718 PMID 28973863 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML