Reflexes of Proto-Ryukyuan *i and *u in Miyakoan as a chain shift

The paper examines conditioned changes that occurred in Miyakoan (mostly Proto-Miyakoan) reflexes of Proto-Ryukyuan close vowels *i and *u after the unconditioned raising of Proto-Ryukyuan *e and *o had taken place. These changes in close vowels are interpreted here as chain shifts. The core assumption is that changes in *i and *u occurred in response to the raising of *e and *o in order to avoid or compensate for the functionally damaging merger of *i/*e and *u/*o