Collective monopole vibrations are studied in the framework of an antisymmetrized version of molecular dynamics as a function of the vibration amplitude. The giant monopole resonance energy in Ca40 is sensitive to the incompressibility of the effective interaction, in good agreement with complete time-dependent Hartree-Fock calculations. The collective response of C12, O16, and Mg24 is also studied. For these lighter nuclei that have an important contribution of an α-clustered component, different frequencies are observed, corresponding to two different types of vibrations associated with breathing and moving of the underlying clusters. Possible connections with direct breakup into α clusters at high excitation energy are discussed.