Notes on the segregates of Acacia farnesiana (L.) Willd. (Fabaceae : Mimosoideae) and related species in North America

摘要

The New World taxa of the AcaciaJhrnesiana (L.) Willd. group (Clarke et al., 1989) range through tropical and subn-opical regions from the southern United States south to central Argentina. Varying from shrubs to small trees, mostly less than 4 m tall, these taxa are usually associated with desert and thorn scrub vegetation, often being dominant members of their respective plant communities. Members of this group are characterized by the following combination of characteristics: involucral bracts at the base of the capitate inflorescence, short shoots just above the stipular spines, and leaves with fewer than 10 pinna pairs. The Acacia farnesiana group in North America is colnposed of 8 taxa distributed among 5 species. The Mexican and Caribbean species of this complex have been studied by Clarke et al. (1989), whereas the United States taxa have been exmnined by Isely (1969, 1973, 1990, 1998). The present study was undertaken to resolve species boundaries while revising the genus Acacia Mill. for the Flora of North America project.