F D such that R 1. Parameter values: identical as in a and B. doi:ten.1371/journal.pcbi.1003778.gcrossing time tm of a metapopulation exhibits a minimum at an intermediate value of D. Indeed, the crossing time on the metapopulation 1st decreases when D is elevated since the minimum crossing time then decreases. But beyond a certain worth of D, the migration rate that yields the highest speedup bec