A phylogenetic analysis and new delimitation of the Neotropical genus Werneria (Compositae, Senecioneae)

Abstract

AbstractThe genus Werneria was first described from six species found in the northern Andes in 1818 by Karl S. Kunth. By 1970 the number of species increased to around 50. Werneria is mostly distributed in the Andean highlands with a single species, W. nubigena, reaching as far as southern Chiapas, Mexico. Today, the genus Werneria encompasses 28 species with its center of diversity located in Peru and Bolivia. It is defined, in part, by having involucral bracts fused at least halfway and lacking a well‐developed calyculus at the base of the head. Further research indicated that there was considerable variability between Werneria species, and several species were transferred into the related genera Anticona, Misbrookea, Senecio, and Xenophyllum. Recently, it has been brought to light that the type of the genus Werneria is W. rigida, an effective lectotypification made by Rockhausen that previous authors working on this group overlooked. Since W. rigida has been accepted so far as a member of the genus Xenophyllum, Rockhausen's typification has resulted in: (1) Xenophyllum a superfluous name for Werneria; (2) Werneria a name to be applied to the species treated thus far as Xenophyllum; and (3) describing the new genus Rockhausenia to place the “traditional” Werneria species. Instead of proposing to conserve the name Werneria to avoid the aforementioned undesirable disruptions in the interest of nomenclatural stability, 30 new combinations have been made. Herein, we present the first comprehensive phylogenetic study based on ITS, trnL, ndhF, matK, and psbA sequence data involving 29 out of the 51 known species of Werneria and Xenophyllum (including the monotypic genus Misbrookea). The results indicate that: (1) the treatment of Misbrookea as a distinct genus is well supported; and (2) Werneria and Xenophyllum are each clearly not monophyletic. This, in addition to the fact that there are no diagnostic morphological synapomorphies to support either of the two genera, suggests treating them as members of a single genus. Moreover, the type of W. subg. Anactis appears to be nested in the genus Senecio. The three species belonging to this subgenus are accordingly transferred to Senecio. Finally, two subgenera are here proposed for facilitating species identification: (1) W. subg. Werneria, including species previously treated under Xenophyllum; (2) W. subg. Rockhausenia comb. & stat. nov., including the “traditional” Werneria species centered around W. nubigena.