Among the Southern Wakashan languages, Ditidaht has patterns of short vowel epenthesis & deletion that are unusually complex. It is shown that the surface presence or absence of short vowels is determined not by their underlying presence or absence, but by how segments are parsed by prosodic constituents. An optimality theoretic analysis is developed, according to which vowel alternations result from the low ranking of faithfulness constraints (MAX/V & DEP/V) relative to constraints on the forms of syllables, feet, & prosodic words. Vowel presence creates ideal iambic feet, makes prosodic words minimally disyllabic, & ensures that adducted consonants (those that involve adducting the vocal folds for glottalization or voicing) are vowel-adjacent. Vowel absence ensures that prosodic words end in consonants, & eliminates unfooted syllables. An additional finding is that all adducted consonants must be postvocalic. Tables, Figures, References. Adapted from the source document