Acacia rigidula (Fabaceae) and related species in Mexico and Texas

Vegetative and floral features of more than 300 specimens of Acacia rigidula and related species were scored and analyzed by Principal Components analysis (PCA) and Stepwise Discriminate Analysis (SDA). The results of these analyses indicate that A. bilimekii, A. brandegeana, and A. rigidula form distinct groups and that two other species, A. californica and A. pringlei, are very similar but distinct from the other three. The data suggest that A. californica and A. pringlei are closely related and probably represent disjunct subspecies of one species. A new combination is hereby proposed: A. pringlei subsp. californica. The results of PCA studies also suggest that plants previously considered as A. conzattii, A. sesquijuga, and A. unijuga are all conspecific with A. pringlei subsp. pringlei and that plants previously considered to be A. sonorensis are conspecific with A. pringlei subsp. californica.