Cellular Basis, Genetic Factors, and Molecular Mechanisms of Hybrid Sterility and Inviability

When species diverge, hybrid offspring that are produced can suffer from reduced fitness. Hybrid fertility and viability are among the affected phenotypes when postzygotic isolation is formed. The cellular basis, genetic factors, and molecular mechanisms of hybrid sterility and inviability are of considerable interest, as they inform our understanding of both speciation and normal fitness. The phenomena of sterility and inviability in interspecies hybrids have been observed for over a century, however, a handful of genes influencing these phenotypes have been identified. Studies have been mainly focused on inter-species hybrids of model species, such as mice and fruit flies, thus limiting our ability to generalize findings to other organisms. Available cytological, genetic, and molecular investigations of hybrids indicate that multiple mechanisms of sterility and inviability are possible. However, identified genetic incompatibilities at similar stages of speciation in different organisms may highlight common patterns in the development of postzygotic reproductive isolation.

The goal of this Research Topic is to cover a wide range of studies related to hybrid sterility and inviability. We invite studies dealing with the problem of causes and consequences with respect to the roles of gene misregulation and genome instability (including roles of transposable elements and small RNAs) in postzygotic isolation. Identification of precise developmental and cellular phenotypes associated with hybrid sterility and inviability in diverse organisms is also important for comparing molecular mechanisms of reproductive isolation across species. Of special interest are manuscripts describing recent advances in genomic sequencing and gene editing that allow looking beyond model organisms in the search for speciation genes and mechanisms of postzygotic reproductive isolation.

This Research Topic welcomes Original Research papers, Reviews, and new ideas related, but not limited, to the following topics:
• Studies of hybrid sterility and inviability in diverse groups of organisms
• Investigation of the cellular basis of hybrid sterility and inviability
• Detailed characterization of the meiotic abnormalities in sterile hybrids
• Genetic and genomic analyses of hybrid sterility and inviability
• Role of genetic variation in the evolution of postzygotic isolation
• Deciphering molecular mechanisms of hybrid sterility and inviability
• Detailed characterization of Dobzhansky-Muller incompatibility genes
• Genetic basis for phenotypic differences between hybrids from reciprocal crosses
• Role of gene misregulation in hybrid sterility and inviability
• Roles of genomic instability and genomic conflict in speciation
• Comparative analysis of mechanisms of postzygotic isolation across species