Since its initial discovery, Mimosa margaritae has been known only from the type, a non-reproductive specimen collected 125 years ago on Margarita Island, off the Pacific coast of Baja California Peninsula. Other specimens from the same Peninsula were mistakenly identified as M. margaritae, but are in fact Mimosa tricephala, one of the closest relatives of M. margaritae. During recent expeditions to the island, M. margaritae was rediscovered. Here, we provide the first description of the flowers and fruits of this species. The taxonomic status of the southern peninsular endemic M. lagunensis is also discussed; we conclude that it should be treated as a variety of M. tricephala, and provide a new combination, M. tricephala var. lagunensis.
