Zulu conjoint/disjoint verb alternation: focus or constituency?

Zulu shows an alternation of conjoint and disjoint (conjunctive/disjunctive, short/long) verb forms. Certain contexts suggest that the distribution of these forms is related to focus. For example, certain adverbial expressions receive a focal interpretation when preceded by a conjoint form but not when preceded by a disjoint form. Similarly, a wh-phrase must be preceded by a conjoint form. This has led some researchers to argue or suggest that the alternation encodes focus directly. This paper examines two different focal hypotheses, one in which a disjoint form encodes focus on the verb and another in which the conjoint form encodes focus on the element following the verb. It is shown that both of these hypotheses are inadequate because certain contexts requiring the conjoint form do not display the predicted focal interpretation. Relativization morphology is argued to also support an analysis independent of focus. It is proposed that the alternation is regulated entirely by the position of the verb within the surface constituencies first proposed in Van der Spuy (1993) and that the associated focal interpretations are the result of a range of interpretations permitted within the different constituencies. Elements remaining within the relevant constituent are nontopical, and focus is one of a range of interpretations they can receive.