Data from: Multispecies interactions shape the transition to multicellularity

This data was collected during the study entitled "Multispecies interactions shape the transition to multicellularity." We explored how interspecific competition shapes the emergence of multicellularity in an experimental system with two yeast species, <em>Saccharomyces cerevisiae</em> and <em>Kluyveromyces lactis</em>, where multicellularity evolves in response to selection for faster settling ability. The experimental design consisted of a 19-day evolution experiment, where cocultures and monocultures of unicellular <em>S. cerevisiae </em>and <em>K. lactis</em> were propagated daily with and without selection for settling (6 replicates each). Cocultures included initial frequencies of 25%, 50%, and 75% <em>K. lactis</em>. Differential growth rates and selection coefficients during the sweep of multicellular <em>K. lactis</em> were calculated, and species frequencies (%) were visualized. We also completed a 20-day evolution experiment with cocultures of multicellular <em>S. cerevisaie</em> and <em>K. lacti</em>s, with each species beginning as rare, transferred with and without settling (6 replicates each). Differential growth rates during the invasion-from-rare experiment were calculated and visualized. To assess the competitive dynamics of the two species before and after the transition to multicellularity, competition assays were performed, with species’ frequencies determined before and after either 24 hours of growth or 7 minutes of settling when each species began as rare. These assays were repeated for unicellular and multicellular isolates. We also obtained 48-hour growth curves for monocultures and 50% cocultures (10 replicates each) and determined the intrinsic growth rate (r) and carrying capacity (K) for each population. Population densities of each species were also measured before and after 24 hours of growth on each species’ spent media.