Species delimitation and recognition in the Pediomelum megalanthum complex (Fabaceae) via multivariate morphometrics

Abstract. Pediomelum is a genus endemic to North America comprising about 26 species, including the megalanthum complex, which consists of Pediomelum megalanthum and its varieties retrorsum and megalanthum, Pediomelum mephiticum, and the recently described Pediomelum verdiense and Pediomelum pauperitense. Historically, species of the megalanthum complex have been variably recognized at the species or variety levels, dependent upon the relative importance of morphological characters as diagnostic of species. Ten quantitative morphological characters regarded as diagnostic at the species level were analyzed using multivariate morphometrics across these taxa in order to examine the discriminatory power of these characters to delineate species and to aid in species delimitation. The analyses support the recognition of Pediomelum megalanthum, Pediomelum mephiticum, and Pediomelum verdiense at the species level, Pediomelum retrorsum as a variety under Pediomelum megalanthum, and suggest the sinking of Pediomelum pauperitense into Pediomelum verdiense. The findings of the present study help quantify the power of certain characters at delimiting taxa and provide a basis for taxonomic revision of the Pediomelum megalanthum complex.