  Risk spreading in bacterial populations is generally regarded as a strategy
to maximize survival. Here, we study its role during range expansion of a
genetically diverse population where growth and motility are two alternative
traits. We find that during the initial expansion phase fast growing cells do
have a selective advantage. By contrast, asymptotically, generalists balancing
motility and reproduction are evolutionarily most successful. These findings
are rationalized by a set of coupled Fisher equations complemented by
stochastic simulations.
