Can sexual selection drive extinction and speciation? A case study in yeast.

Sexual selection describes the suite of evolutionary processes that lead to differential mating success among individuals in a population. Sexual selection is predicted to impact populations over time in two primary ways. First, strong sexual selection pressures are thought to predispose populations to extinction, as sexually selected traits are inherently costly. Second, sexual selection can accelerate the possibility for pre-zygotic isolation between temporarily separated populations, thus promoting speciation. Though many previous studies have attempted to document whether these theoretical predictions are fulfilled, all have rely on indirect approaches and have yielded mixed results. Here, I use a model organism, the yeast Saccharomyces cerevisiae, to experimentally test these predictions by directly manipulating the strength of sexual selection among replicate populations. I found some evidence that sexual selection may make a population less resistant to extinction, though this was not equivocal. Importantly, there was much greater variation in resistance to extinction between populations subjected to strong sexual selection pressures compared to controls. I was unable to assay speciation potential. Importantly, I was able to design a system where this question could be tested more thoroughly in the future. Results of more detailed analyses would have important implications in conservation, understanding the fossil record, and explaining the genesis of new species