Resource distribution unifies optimal offspring size and bacterial aging

Abstract

How should a parent optimally distribute limited resources among its offspring? This question is as relevant to a mother bird deciding how to allocate food among her chicks as it is to a bacterium dividing high-quality organelles between its daughters. Optimal offspring size theory has long explored the tradeoff between the number and size of off-spring in higher organisms. Meanwhile, the emerging field of bacterial aging examines when cells evolve unequal sharing of old cellular components. Our study unifies these two disciplines through a model of resource allocation. This model highlights that the convexity of how resources affect offspring survivorship determines whether even or uneven resource distribution evolves. Based on this, we derive the optimal resource distribution strategies, show that they evolve, and characterize when these strategies are robust to fluctuating environments. These results not only agree with and strengthen existing models, but also provide an organizing framework that enables new predictions. These include the conditions which select for strategies that contain a”runt of the litter.”