Automorphism-primal algebras generate verbose varieties

A finite algebra is called automorphism-primal if its clone of term operations coincides with all operations that preserve its automorphisms. We prove that the variety generated by an automorphism-primal algebra is verbose, that is, on every member algebra, every fully invariant congruence is verbal. The proof is a nice application of the theory of natural dualities as developed by Davey et al.