Until recently, our understanding of the genetics of speciation was limited to a narrow group of model species with a specific set of characteristics that made genetic analysis feasible. Rapidly advancing genomic technologies are eliminating many of the distinctions between laboratory and natural systems. In light of these genomic developments, we review the history of speciation genetics, advances that have been gleaned from model and non-model organisms, the current state of the field, and prospects for broadening the diversity of taxa included in future studies. Responses to a survey of speciation scientists across the world reveal the ongoing division between the types of questions that are addressed in model and non-model organisms. To bridge this gap, we suggest integrating genetic studies from model systems that can be reared in the laboratory or greenhouse with genomic studies in related non-models where extensive ecological knowledge exists.

The significance of prezygotic isolation for speciation has been recognized at least since the Modern Synthesis. However, fundamental questions remain. For example, how are genetic associations between traits that contribute to prezygotic isolation maintained? What is the source of genetic variation underlying the evolution of these traits? And how do prezygotic barriers affect patterns of gene flow? We address these questions by reviewing genetic features shared across plants and animals that influence prezygotic isolation. Emerging technologies increasingly enable the identification and functional characterization of the genes involved, allowing us to test established theoretical expectations. Embedding these genes in their developmental context will allow further predictions about what constrains the evolution of prezygotic isolation. Ongoing improvements in statistical and computational tools will reveal how pre- and postzygotic isolation may differ in how they influence gene flow across the genome. Finally, we highlight opportunities for progress by combining theory with appropriate data.