NEW DISTRIBUTION RECORDS FOR GAMOCHAETA (ASTERACEAE: GNAPHALIEAE) IN THE UNITED STATES

Gamochaeta stagnalis is reported for the first time for the United States (Arizona and New Mexico). In Arizona these plants have previously been identified as Gamochaeta purpurea and Gamochaeta falcata. The species is common in Mexico and apparently is at the northern limit of its distribution in Cochise, Pima, and Santa Cruz cos., Arizona, and Hidalgo Co., New Mexico. Gamochaeta purpurea sensu stricto also occurs in Arizona, disjunct from its main range in the eastern U.S.A. Plants of the southeastern U.S.A. previously identified in some treatments as Gamochaeta falcata are separated into two species: Gamochaeta calviceps and Gamochaeta antillana. A lectotype is chosen for G. antillana. Gamochaeta calviceps is known primarily from the southeastern U.S.A. but is reported from two collections in California. Gamochaeta coarctata is first reported for Arkansas and Virginia and further documented for California. Gamochaeta stachydifolia, a South American native, is reported from two counties in California. For each of the 12 Gamochaeta species recorded for the U.S.A., a hypothesis of nativity is given, with a brief rationale.