“Speciation” was a “speculation” two decades ago. Thanks to the recent advance of molecular biology techniques and genomic sequencing of species satellite to model organisms, detailed study of speciation is becoming feasible in many animal and plant groups. In fact, a dozen of “speciation genes” responsible for reproductive isolation between sibling species have been identified at the molecular level. Further, genetic changes leading to morphological differentiation among related species have been elucidated, supported by phylogenetic analyses in high resolution. We invite investigators to contribute original research articles as well as review articles that will stimulate the continuing efforts to understand speciation and species differentiation not only of genetic mechanisms but also of ecological and evolutionary causes. Potential topics include, but are not limited to:

• Hybrid sterility and inviability
• Sexual isolation
• Gametic isolation
• Comparative genomics
• Morphological, physiological, or behavioral differentiation
• Phylogenetic approach on speciation study
• Ecological speciation

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