Life history evolution and the origin of multicellularity: the case of different types of cells

TL;DR

This paper models the evolution of cell differentiation in multicellular colonies, considering environmental energy constraints, and shows how different cell types can optimize colony fitness through specialization or generalism.

Contribution

It introduces a robust model incorporating environmental factors and energy restrictions to explain cell differentiation and specialization in multicellularity.

Findings

Differentiation tends to full specialization under linear trade-offs.

Environmental energy restrictions lead to multiple optimal states.

Cell types can be specialized or unspecialized with limited ranges of viability and fecundity.

Abstract

The problem of unicellular-multicellular transition is one of the main issues that is discussing in evolutionary biology. In [1] the fitness of a colony of cells is considered in terms of its two basic components, viability and fecundity. Intrinsic trade-off function of each cell defines a type of cell. We elaborate models providing in [1]. Assuming that all intrinsic trade-off functions are linear, we construct a model with different cell types and show that the differentiation of these types tends to full specialization. In addition, we attempt to consider the fact that environmental factors influence on the fitness of the colony. Thus, we introduce an energy restriction to the model and show that in optimum we get situations in which there exists a set of states, each of them allowing colony to achieve the same maximum level of fitness. In some states arbitrary chosen cell may be specialized, in some - unspecialized, but fecundity and viability of each cell belong to limited ranges (which are unique for each cell). It is worth pointing out that the models from [1] are not robust. We try to overcome this disadvantage.