Pappus Bristles Research Articles

Charadranaetes, a New Genus of the Senecioneae (Asteraceae) from Costa Rica

A new genus of the Senecioneae, Asteraceae, from Costa Rica, Charadranaetes, is described based on Senecio durandii Klatt, characterized by an obnoxious odor emitted by crushed parts, elongate linear corolla lobes that are not recurved, and a prominently rounded style apex that bears little or no apical coma. A key to the genera of Senecioneae in Costa Rica is furnished. The purpose of this paper is to describe a new genus, Charadranaetes, based on the single species Senecio durandii of Costa Rica. The species was based by Klatt (1892) on a collection from near Volcain Barba in the Province of Heredia, Costa Rica. Generic position was not in question, since Senecio traditionally grew to include approximately 3400 species of diverse form and distribution defined by principal involucral bracts in a single series, a small but distinct calyculus, and a pappus of abundant capillary bristles. The species has since been noted as anomalous by numerous botanists but has continued by default to be included in the overly broad concept of Senecio because of its capillary pappus, yellow rays, and blunt style tips. The present study relies on recent progress in the understanding of the tribe Senecioneae, as reviewed below, and offers some additional evidence illustrated by scanning electron micrograph (SEM) study of pollen (Figs. 1-7) raphides of the gynoecium (Fig. 8), and number of rows of pappus bristles (Figs. 9, 10). Early efforts at division of Senecio in North and Central America were mostly infrageneric (Greenman, 1901, 1916), and Greenman, the well-known authority in the genus, was credited by Standley (1938) with referring S. durandii to his section Streptothamni, a subgroup of vines now treated in the segregate genus Pentacalia (Robinson & Cuatrecasas, 1978). Standley, in his Flora of Costa Rica (1938) stated that . .. this species is a most distinct one, altogether unlike any other with which I am familiar. He further added that Senecio durandii has little if anything in common with other species grouped in the section Streptothamni of Greenman. More recently, Barkley et al. (1996) left S. durandii as a species within Senecio sensu stricto whose accurate taxonomic disposition had yet to be ascertained. Previous subdivisions of Senecio at the generic level have not included the Costa Rican S. durandii. It was not among the genera with pointed style tips such as Gynoxys Cassini or Pseudogynoxys (Greenman, 1916, as subgenus; Cabrera, 1950, Cuatrecasas, 1955, and Robinson & Cuatrecasas, 1977, as genus). Senecio durandii was not in the distinctive tussilagionoid (cacalioid) lineage mostly of East Asia and Mexico that is distinct by cylindrical anther collars, continuous stigmatic surfaces, and a chromosome base number of x = 30 (Robinson & Brettell, 1973, 1974). As noted above, the Costa Rican species did not belong to the scandent or heath-like genus Pentacalia (Robinson & Cuatrecasas, 1978). Dresslerothamnus Robinson (1989) is from Panama and adjacent areas, but it differs by the scandent or scrambling habit and complex T-shaped hairs. The nearest likely relatives, Jessea and Talamancalia (Robinson & Cuatrecasas, 1994), still were not considered to include Senecio durandii. The present new genus, Charadranaetes, cannot be included in Senecio, which is typified by the European native and widely adventive species Senecio vulgaris L. The latter species and its closest relatives are rosettiform herbs with decrescent upper foliage, fistulose receptacles, short recurved corolla lobes, and truncate style tips without an apical coma. The most typical elements of Senecio also have enlarged plate-like raphides in the cells of the ovule (Fig. 8). Senecio durandii is a semi-woody to woody, decumbent to somewhat erect subshrub with non-decrescent foliage, solid receptacles, linear and non-recurved corolla lobes, and a prominently NovoN 7: 162-168. 1997. This content downloaded from 157.55.39.178 on Fri, 05 Aug 2016 05:10:50 UTC All use subject to http://about.jstor.org/terms Volume 7, Number 2 1997 Janovec & Robinson 163 Charadranaetes (Asteraceae) from Costa Rica

A New Species of Perityle (Asteraceae) from Southwestern Chihuahua, Mexico

Perityle vigilans is described from the Sierra Madre Occidental of southwestern Chihuahua. It differs from other Perityle by the combination of its white ligules, sparsely setose- hispid achenes, finely grayish-villosulous tomentum, and absence of pappus bristles. The new species is believed to be most closely related to P. rosei and P. trichodonta, which occur about 800 km to the south. A key is presented that distinguishes the 12 known taxa of Perityle occurring in the northern Sierra Madre Occidental, an area of high diversity in the genus.