Comments: Includes diazi group, formerly regarded as a separate species (AOU 1998). A. fulvigula, A. rubripes, A. wyvilliana, A. laysanensis, and some Old World forms sometimes are included in this species (AOU 1983, 1998). Allozyme data presented by Browne et al. (1993) indicate that A. platyrhynchos is specifically distinct from wyvilliana and laysanensis. Mitochondrial DNA data indicate an extremely close evolutionary relationship between mallards and black ducks, and, in conjunction with geographic distributions, suggest that the black duck is a recent evolutionary derivative of a more broadly distributed mallard-black duck ancestor (Avise et al. 1990). See Livezey (1991) for a phylogenetic analysis and classification (supergenera, subgenera, infragenera, etc.) of dabbling ducks based on comparative morphology. See Byers and Cary (1991) for information on morphological differences among wild, urban, and game-farm mallards.