  We derive the Jeffreys prior for the parameter of the Multivariate Ewens
Distribution and study some of its properties. In particular, we show that this
prior is proper and has no finite moments. We also investigate the impact of
this default prior on the a priori distribution of the number of species and
the a priori probability of discovery of a new species, which are usually
employed in subjective prior elicitation. The effect of the Jeffreys prior for
posterior inference is illustrated using examples arising in the context of
inference for species sampling models and Dirichlet process mixture models.
