Abstract

Co-authors: Thomas Garcia (IBENS, Paris), Paul Rainey (NZIAS, Auckland/MPI, Ploen)

Microbial populations display a number of collective forms of organization, some of which have been integrated into complex life cycles. For instance, clusters or flakes of cells confer protection against stress to yeast and bacteria, swarming powers collective foraging in Myxobacteria, and recurrent aggregation of sparse cells allows the development of fruiting bodies in Myxobacteria and social amoebas. In this talk, I will present different ways natural selection can drive the evolution of groups composed of replicating particles. In particular, I will focus on settings when collectives are composed of particles of two types, which provide different contributions to collective functionality. A classical conundrum associated with such systems is that functional collectives exist, in spite of the disruptive effects of free-riding on groups composed of cooperative particles. I will use mathematical models that take explicitly into account the process of group formation to show that the evolution of functional collectives can stem from simple features of the composing particles, such as differential stickiness. However, something more is required if selection is to shift to the collective level. In concluding, I will discuss the value of a mechanistic perspective on the evolutionary emergence of multicellular life forms.