Mate-recognition and species boundaries in the ascomycetes

Reproductive gene evolution is commonly invoked as a source of reproductive isolation during speciation. This possibility has not been adequately explored in the Ascomycota, the most species-rich fungal phylum. The mechanisms of mate-recognition in this group are relatively simple: a mating type locus determines reproductive mode and sexual compatibility, and two pheromone/receptor pairs control sexual attraction. However, ascomycete reproductive genes can experience unique and interesting evolutionary forces, which could lead to rapid divergence. In this review, we examine the mechanisms of sexual interaction in ascomycetes and explore current evidence as to whether these mechanisms allow for species-specificity in mate-recognition. We discuss the evolutionary forces that can drive reproductive gene divergence, how these may apply in the world of ascomycetes, and their possible consequences for speciation.