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Abstract

Meiosis in Saccharomyces yeast produces four haploid gametes that usually fuse
with each other, an extreme form of self-fertilization among the products of a
single meiosis known as automixis. The gametes signal to each other with sex
pheromone. Better-quality gametes produce stronger signals and are preferred
as mates. We suggest that the function of this signalling system is to enable
mate choice among the four gametes from a single meiosis and so to promote
the clearance of deleterious mutations. To support this claim, we construct a
mathematical model that shows that signalling during automixis (i) improves
the long-term fitness of a yeast colony and (ii) lowers its mutational load. We
also show that the benefit to signalling is greater with larger numbers of
segregating mutations