Systematics of North American Froelichia (Amaranthaceae subfam. Gomphrenoideae) I: Identification of consistent morphological variation and segregation of species complexes

Abstract

Phenetic analyses of morphological variation were used to elucidate distinctiveness and circumscription of taxa within, the genus Froelichia in North America. Preserved specimens representing all recognized taxa and one suspected hybrid taxon were measured for 39 continuous and discrete characters and subjected to univariate and multivariate analyses. Principal coordinate analysis indicated the presence of three distinct groups of species with intergradation of morphological intermediates. Two of the groups corresponded to two large complexes of species, the F. floridana complex of the south-central and southeastern United States and the F. interrupta complex, principally of Mexico, while the third consisted of F. gracilis native to the southern United States and adjoining Mexico. Discriminant analysis on each of the two complexes indicated morphologically distinct forms within each morphologically variable complex. The use of novel characters for the discrimination of taxa resulted in the identification of less plastic traits among the recognized species. Use of these newly discovered traits provides more reliable means for the identification of taxa. An instance of potential, hybridization among three taxa in southern Texas was additionally explored with the putative hybrid taxa exhibiting an intermediate combination of morphological traits between each of the putative parents.