A New Weed in Florida, Spermacoce latifolia, and the Distinction between S. alata and S. latifolia (Spermacoceae, Rubiaceae)

Spermacoce alata Aubl. and Spermacoce latifolia Aubl., frequently referred to as Borreria alata (Aubl.) DC. and Borreria latifolia (Aubl.) K. Schum., were described in the 18th century by Jean Baptiste Christophe Fusee Aublet from French Guiana. They have sometimes been treated as a single species but are two easily distinguished species. Spermacoce alata occurs from Venezuela through the Guianas and in the eastern Amazon basin north of the Rio Amazonas and is not weedy. The New World distribution of S. latifolia is from southern Mexico through Central America and throughout eastern South America to Bolivia and Paraguay, and it is naturalized in the tropical and subtropical regions of the Old World. Spermacoce latifolia is a noxious weed that has frequently been misidentified as S. alata. The first documented reports of S. latifolia in Florida are presented. Given its aggressive colonization elsewhere, prompt consideration should be given to controlling the spread of S. latifolia in the southern USA.