Genome-wide mapping in a house mouse hybrid zone reveals hybrid sterility loci and Dobzhansky-Muller interactions.

Leslie M Turner,Bettina Harr

doi:10.7554/elife.02504

Abstract

Mapping hybrid defects in contact zones between incipient species can identify genomic regions contributing to reproductive isolation and reveal genetic mechanisms of speciation. The house mouse features a rare combination of sophisticated genetic tools and natural hybrid zones between subspecies. Male hybrids often show reduced fertility, a common reproductive barrier between incipient species. Laboratory crosses have identified sterility loci, but each encompasses hundreds of genes. We map genetic determinants of testis weight and testis gene expression using offspring of mice captured in a hybrid zone between M. musculus musculus and M. m. domesticus. Many generations of admixture enables high-resolution mapping of loci contributing to these sterility-related phenotypes. We identify complex interactions among sterility loci, suggesting multiple, non-independent genetic incompatibilities contribute to barriers to gene flow in the hybrid zone.

Highlights

New species arise when reproductive barriers form, preventing gene flow between populations (Coyne and Orr, 2004)
We investigated two phenotypes in males from the house mouse hybrid zone: relative testis weight and genome-wide testis gene expression pattern
Genetic mapping of testis weight and testis gene expression in hybrid zone mice implicated multiple autosomal and X-linked loci and a complex set of interactions between loci. These results provide insight into the genetic architecture of a reproductive barrier between two incipient species in nature

Summary

Introduction

New species arise when reproductive barriers form, preventing gene flow between populations (Coyne and Orr, 2004). ‘islands of divergence’ have been reported in species pairs from taxonomically diverse groups (Turner et al, 2005; Nadeau et al, 2011; Nosil et al, 2012; Ellegren et al, 2013; HemmerHansen et al, 2013; Renaut et al, 2013; Carneiro et al, 2014; Poelstra et al, 2014; Schumer et al, 2014). These high-divergence genomic outlier regions are sometimes referred to as ‘islands of speciation’, resistant to introgression because they harbor genes causing reproductive isolation. Other forces can create similar genomic patterns, islands may not always represent targets of selection that contributed to speciation (Noor and Bennett, 2009; Turner and Hahn, 2010; Renaut et al, 2013; Cruickshank and Hahn, 2014)

Methods

Results

Conclusion