Glittering gold and the quest for Isla de Muerta

The interpretation of patterns of divergence between related species across the genome is complex, and many of these complications are clearly reviewed in the article by Ravinet et al. (2017). Indeed, such a review is timely and clarifies much of the confusion about what can, and cannot, be inferred from such genome scans. Although the authors state that ‘We argue one of the principal aims of the field is to identify the barrier loci involved in limiting gene flow’, they also show how genome data can be used to investigate the genetic architecture of speciation without identifying individual barrier loci. We will argue that in many cases, the identification of barrier loci based on genomic data alone will be extremely challenging or impossible, and that it can be equally valuable to characterize general features of species barriers, such as their architecture and evolution through time. We caution against an obsession with the identification of functional loci that might distract researchers from addressing the many other exciting questions in speciation that do not require such specific information.