Caroline Rose, New Zealand Institute for Advanced Study, Massey University
I will describe an experiment in which we witness the emergence of Darwinian individuality in populations of cooperating bacteria subjected to a selective regime that rewards collective-level fecundity. Central to collective reproductive success is a primitive life cycle that is fueled by conflict between cooperators and cheats. Enhanced fitness of derived collectives is attributable to a property selected at the collective-level, namely, the capacity to transition through phases of a life cycle, and is not explained by improvement in individual cell fitness. Indeed, the fitness of individual cells declined. The experiment provides a simple mechanism for the evolution of collective-level reproduction and shows this innovation to be sufficient for the decoupling of lower- and higher-level fitness as is anticipated during a transition in individuality.