Variation at an adhesin locus suggests sociality in natural populations of the yeast Saccharomyces cerevisiae

Microbes engage in numerous social behaviors that are critical for survival and reproduction, and that require individuals to act as a collective. Various mechanisms ensure that collectives are composed of related, cooperating cells, thus allowing for the evolution and stability of these traits, and for selection to favor traits beneficial to the collective. Since microbes are difficult to observe directly, sociality in natural populations can instead be investigated using evolutionary genetic signatures, as social loci can be evolutionary hotspots. The budding yeast has been studied for over a century, yet little is known about its social behavior in nature. Flo11 is a highly regulated cell adhesin required for most lab social phenotypes; studies suggest it may function in cell recognition and its heterogenous expression may be adaptive for collectives such as biofilms. We investigated this locus and found positive selection in the areas implicated in cell-cell interaction, suggesting ...