Abstract

Despite the economic importance and longstanding worldwide commercialization of representatives of the Beaucarnea lineage, it remains poorly known systematically. One of the main systematic problems is lack of certainty regarding the validity of the genus itself. Some authors consider Beaucarnea a synonym of its close relative Nolina, whereas others consider Beaucarnea a distinct genus. In addition to the Beaucarnea vs. Nolina controversy, the boundary between Beaucarnea and Calibanus is an issue that has not yet been addressed. Here we show that Beaucarnea is a well-supported entity, distinct from Nolina on molecular and morphological grounds. Additionally, we demonstrate the absence of reciprocal monophyly between Beaucarnea and Calibanus and formally include Calibanus within Beaucarnea. These decisions were based on maximum parsimony, Bayesian, and maximum likelihood analyses of datasets including ten species of Beaucarnea, two species of Calibanus, six species of Nolina, and five species of Dasylirion, with sequences from the nuclear ITS and plastid trnL-F and ycfl regions. Our taxonomic decisions were also based on morphological observations of herbarium specimens and on the literature. We illustrate the diagnostic features of the genera with phylogenetic character mapping. Finally, we offer a redescription of Beaucarnea to accommodate the former Calibanus species and give a key to the taxonomically valid Beaucarnea species.