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Abstract

Whole-genome duplication has shaped the genomes of extant lineages ranging from unicellular fungi to vertebrates, and its association with several species-rich taxa has fuelled interest in its potential as a catalyst for speciation. One well-established model for the evolution of reproductive isolation involves the reciprocal loss of redundant genes at different loci in allopatric populations. Whole-genome duplication simultaneously doubles the entire gene content of an organism, resulting in massive levels of genetic redundancy and potential for reciprocal gene loss that may produce postzygotic reproductive isolation. Following whole-genome duplication, different populations can potentially change or lose gene function at different duplicate loci. If such populations come back into contact any F1 hybrids that are formed may suffer reduced fertility as some of the gametes they produce may not carry a full complement of functional genes. This reduction in hybrid fertility will be directly proportional to the number of divergently resolved loci between the populations. In this work, we demonstrate that initially identical populations of allotetraploid yeast subjected to mutagenesis rapidly evolve postzygotic reproductive isolation, consistent with the divergent loss of function of redundant gene copies.