Pronominal indexing and the changing face of Austronesian voice

Sipora Mentawai (SM) shows a restructured Malayo-Polynesian Western Region voice system in which inherited Actor Voice (AV) morphology is retained but no longer supports a productive reduced ‘Indonesian-type’ AV/UV alternation. Instead, the language occupies a semi-alternating position on an alternation continuum: residual voice material persists, alongside TAM and information-structure correlates, but there is no longer an alternation between two grammatical voices; only between AV and non-voice-marked verbs, which in main clauses are, save some edge cases, obligatorily marked for agreement. AV m- assigns SUBJ to the ACTOR macrosemantic role; ensures it has a privileged position in the information structure; and assigns REALis mood to verbs on which it appears. Agreement morphology can be either grammatical or anaphoric, and carries no mood assignment. This account presents a detailed and novel case of how reduced ‘Indonesian-type’ voice systems are subject to attrition into ‘semi-alternating’ systems.