Hypermutability causes divergent adaptation accross population sizes
We show that mutation biases steer bacterial populations toward highly divergent, minimally overlapping molecular paths to antibiotic resistance. Replicating the same adaptation experiment with two mutators across five population sizes spanning a 100-fold range revealed clear signatures of mutation-driven adaptation, even in large populations. Importantly, these divergent evolutionary paths have tangible consequences, leading to markedly different collateral sensitivities to other antibiotics.