Abstract
Mòcheno, a German variety spoken in Trentino (Italy), displays an interesting case of phonologically conditioned suppletive allomorphy in past participle formation. Past participle formation involves a variety of strategies, from absence of a prefix, to affrication, to prefixing a CV-prefix ga-. I propose that two allomorphs are involved in the process, a subsegment [-cont, -voice] and a prefix ga- and that the distribution of the two allomorphs is regulated by a hierarchy of wellformedness constraints. This hierarchy in turn consists of two independent partial hierarchies, which are active in the grammar of the language in general, where they are responsible for morphoprosodic alignment at left stem edges and for the distribution of obstruents, respectively. This means that Mòcheno past participles give us evidence in favor of the hypothesis that allomorph selection can, and sometimes must, be interpreted in terms of optimization. By adopting an alternative analysis in terms of subcategorization of the allomorphs for a certain phonological context, the relationship between the distribution of past participle allomorphs and other pieces of the Mòcheno grammar would remain completely opaque.