The Antioch Dunes Evening Primrose (Oenothera deltoides spp. howellii) was federally listed as endangered in 1978. Its naturally occurring population is confined to the two disjunct units of the refuge, and the adjacent PG&E and Kemwater lands.
The Contra Costa wallflower (Erysimum capitatum spp. angustatum) is in the same family as the mustard family, Brassicaceae. The wallflower was listed as endangered in 1978. The entire known wild population of the wallflower consists at the refuge and adjacent PG&E and Kemwater lands.
The Lange's metalmark (Apodemia mormo langei) butterfly was first discovered in 1933 and was described five years later. In June 1976, this local subspecies was one of the first eight insects to be listed as endangered under the Endangered Species Act of 1973.
Naked-stemmed buckwheat (Eriogonum nudum var. psychicola) is so named because it has very few leaves along its bare stems. This species the only plant the Lange's metalmark butterfly will lay its eggs on, and is the food plant for the Lange's metalmark butterfly larvae.