A suppletion-pattern gap in 'tripartite' tense-aspect systems

The present paper identifies a new gap in tense-aspect suppletion patterns in Indo-European 'tripartite' tense-aspect systems: For any triple of present-imperfect-aorist forms, the present and aorist forms never share the same base to the exclusion of the imperfect form. I explore the analysability of the relevant gap as a 'containment-and-competition' gap, i.e. in terms of Bobaljik's (2012) *ABA, or, alternatively, as a 'structure-and-locality' gap, i.e. in terms of Bobaljik's *AAB. I argue that, though the present-imperfect-aorist triple does not plausibly meet the morphosyntactic eligibility criteria for the former type of analysis, it does for the latter, once we allow for a specific kind of structural variation across tripartite tense-aspect systems. These conclusions suggest that there are domains in which 'structure-and-locality' gaps arise in the absence of 'containment-and-competition' gaps.