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Free keywords:
body size; cell size; mate choice; mating; Saccharomyces cerevisiae; sexual selection
Abstract:
In unicellular organisms like yeast, mating with the right partner is critical to future fitness because each individual can only mate
once. Because cell size is important for viability, mating with a partner of the right size could be a significant advantage. To investigate
this idea, we manipulated the size of unmated yeast cells and showed that their viability depended on environmental conditions; large
cells do better on rich medium and small cells do better on poor medium. We also found that the fitness of offspring is determined by
the size of their parents. Finally, we demonstrated that when a focal cell of one mating type was placed with a large and a small cell of
the opposite mating type, it was more likely to mate with the cell that was closer to the optimum size for growth in a given environment.
This pattern was not generated by differences in passive mating efficiency of large and small cells across environments but by competitive
mating behavior, mate preference, or both. We conclude that the most likely mechanism underlying this interesting behavior is
that yeast cells compete for mates by producing pheromone signals advertising their viability, and cells with the opportunity to choose
prefer to mate with stronger signalers because such matings produce more viable offspring.
