PT  - JOURNAL ARTICLE
AU  - Daniel L. Powell
AU  - Ben Moran
AU  - Bernard Kim
AU  - Shreya M. Banerjee
AU  - Stepfanie M. Aguillon
AU  - Paola Fascinetto-Zago
AU  - Quinn Langdon
AU  - Molly Schumer
TI  - Two new hybrid zones expand the swordtail hybridization model system
AID  - 10.1101/2020.11.18.389205
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.11.18.389205
4099  - http://biorxiv.org/content/early/2020/11/20/2020.11.18.389205.short
4100  - http://biorxiv.org/content/early/2020/11/20/2020.11.18.389205.full
AB  - Natural hybridization events provide unique windows into the barriers that keep species apart as well as the consequences of their breakdown. Here we characterize hybrid populations formed between the northern swordtail fish Xiphophorus cortezi and X. birchmanni from collection sites on two rivers. We develop sensitive and accurate local ancestry calling for this system based on low coverage whole genome sequencing. Strikingly, we find that hybrid populations on both rivers consist of two genetically distinct subpopulations: a cluster of nearly pure X. birchmanni individuals and one of phenotypically intermediate hybrids that derive ~85-90% of their genome from X. cortezi. Simulations and empirical data suggest that at both sites initial hybridization occurred ~150 generations ago, with little evidence for contemporary gene flow between subpopulations, likely due to strong assortative mating. The patterns of population structure uncovered here mirror those seen in hybridization between X. birchmanni and its sister species, X. malinche. Future comparisons will provide a window into the repeatability of the outcomes of hybridization not only across independent hybridization events between the same species but also across distinct species pairs.Competing Interest StatementThe authors have declared no competing interest.