  We propose a mechanism to explain the fluctuations of the ground state energy
in quantum dots in the Coulomb blockade regime. Employing the random matrix
theory we show that shape deformations may change the adjacent peak spacing
distribution from Wigner-Dyson to nearly Gaussian even in the absence of strong
charging energy fluctuations. We find that this distribution is solely
determined by the average number of anti-crossings between consecutive
conductance peaks and the presence or absence of a magnetic field. Our
mechanism is tested in a dynamical model whose underlying classical dynamics is
chaotic. Our results are in good agreement with recent experiments and apply to
quantum dots with spin resolved or spin degenerate states.
