Cohen and Schenk (2021) Data from: Investigating phylogenetic placement and species-level relationships in a recent radiation of Mentzelia section Bartonia (Loasaceae) from the Mojave Desert

Understanding species level relationships is a central goal in systematic botany; however complexes of closely related and morphologically similar species often pose considerable challenges to that goal. The North American west is home to many notable genera that notoriously have difficult species complexes (e.g., Astragalus, Eriogonum, Penstemon). Mentzelia section Bartonia (Loasaceae) is a recently evolved and diverse clade that occurs across the North American west. Phylogenetic studies have resolved many relationships, but the relationships within a species complex of perennial, subshrub species that occurs in the Mojave Desert, Great Basin, and Colorado Plateau remains elusive. This arid-adapted clade, which is referred to as the Mojave clade, has significant conservation implications, due to three narrowly endemic species:  Mentzelia polita and Mentzelia tiehmii are state listed, and Mentzelia leucophylla is federally listed. Species relationships within the Mojave clade are not f...