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I had always seen evolutionary potential as being the result of a population having greater within-population genetic variation. By chance such a population is more likely to contain alleles that code of traits that might give their holders greater fitness under a new set of conditions. Such a population would then evolve in response to selection. A population with fewer alleles would not have the opportunity. The same could occur through drift rather than selection?? This evolutionary potential is of course possible among populations, so that a species with greater evolutionary potential is one with overall greater diversity. In this case selection would be more about sorting among populations. Paul's comment reminded me of the importance of time scale. PERSISTENCE might allow for rise in variation through mutation. However, this will depend on the fact that new alleles are not lost through drift. In small populations accumulation of such variation might me hard.

Neal Williams