DNA sequence data use in phylogenetic analysis of eastern North American stitchworts

Generic delimitation in Caryophyllaceae has been a challenge, and has been informed most recently by use of molecular phylogenetic data. In this study, analysis of 29 samples from the small segregate Mononeuria using nuclear ITS and plastid rps16 data revealed it to be polyphyletic. The type species Mononeuria patula as well as two others (M. muscorum and M. paludicola) were shown to belong to the Sabulina clade. The remaining species formed a clade that also included the previously monotypic Geocarpon and was sister to a heterogeneous group that included the Hawaiian Schiedea and three other monotypic genera, Honckenya, Wilhelmsia, and Triplateia. Although several nomenclatural options are available, we propose to place the species from this clade into a single genus, Geocarpon, which basically follows the most recent treatment after exclusion of Sabulina species, but with the necessary new genus placements. New combinations are proposed: Sabulina muscorum, Sabulina paludicola, Geocarp...