Pre-zygotic isolation in the macroalgal genusFucus from four contact zones spanning 100–10 000 years

Abstract

Hybrid zones provide an ideal natural experiment to study the selective forces driving evolution of reproductive barriers and speciation. If hybrid offspring are less fit than the parental species, pre-zygotic isolating barriers can evolve and strengthen in response to selection against the hybrids (reinforcement). Four contact zones between the intertidal macroalgae Fucus serratus (Fs)andFucus distichus(Fd), characterized by varying times of sympatry and order of species introduction provide an opportunity to investigate reinforcement.