Lower conversion rates can buffer the effects of drugs. (a) Optimal constant conversion rates in the face of drug treatment (labelled as doses in mg/kg) are lower than in the absence of drugs. (b) As expected, drug treatment reduces parasite fitness (i.e., cumulative transmission potential). Grey bars indicate fitness when parasites are constrained to the drug‐free optimal conversion rate (~0.42). Black bars show the fitness gains achieved by adopting the dose‐specific optimal conversion rate (from A). With lower conversion rates, parasites are able to recoup some of the fitness that is lost due to drugs