Phylogenetic reconstruction of Mentzelia section Bicuspidaria (Loasaceae) based on plastid and nuclear ribosomal DNA sequences.

• In Event: Botany Oral Session & Section Meeting

Abstract

Mentzelia section Bicuspidaria is a group of desert annuals containing five taxa distributed in northwestern Mexico and the southwestern United States. Here we present the first fully resolved phylogenetic reconstruction of Bicuspidaria based on plastid and nuclear ribosomal DNA sequences. Reconstructions suggest two major clades within Bicuspidaria. The ‘northern Bicuspidaria clade’ composed of M. reflexa, M. tricuspis, and M. tridentata is endemic to the southwestern United States. The ‘southern Bicuspidaria clade’ is composed of M. hirsutissima and M. involucrata, species distributed on both sides of the Mexico-United States border. Furthermore, reconstructions based on both plastid and nuclear markers suggest that M. hirsutissima is paraphyletic with respect to M. involucrata. These two clades of M. hirsutissima populations are distinguished most reliably by geography. The ‘northern M. hirsutissima clade’ occurs in southern California and Baja California and is sister to M. involucrata. The ‘southern M. hirsutissima clade’ has been found only in Baja California Sur and Cedros Island at the southwestern tip of Baja California. Further work is needed to determine the taxonomic status of these previously unrecognized clades.

Authors

• Joshua M. Brokaw, Abilene Christian University

• John J. Schenk, Georgia Southern University