NUTRIENT STARVATION. “Complex ecologies also evolve in closed cultures in which the nutrients are exhausted and are not renewed. In these cultures, the viable cell population declines over time, as starvation takes its toll. However, not all genotypes die at the same rate, and the survivors are enriched for growth advantage in stationary phase (GASP) mutants, that exploit by-products of dead and dying cells.”
https://www.nature.com/articles/nrg3564