  We examine the lowest excitations of one-dimensional few-boson systems
trapped in double wells of variable barrier height. Based on a numerically
exact multi-configurational method, we follow the whole pathway from the
non-interacting to the fermionization limit. It is shown how, in a purely
harmonic trap, the initially equidistant, degenerate levels are split up due to
interactions, but merge again for strong enough coupling. In a double well, the
low-lying spectrum is largely rearranged in the course of fermionization,
exhibiting level adhesion and (anti-)crossings. The evolution of the underlying
states is explained in analogy to the ground-state behavior. Our discussion is
complemented by illuminating the crossover from a single to a double well.
