Roldana riparia is described from Huehuetenango, Guatemala (Municipio de Chiantla). The genus Roldana is abundant in montane forests of Guatemala (nine species) and the new species is endemic to the Sierra Cuchumatanes.
In 2009, the authors discovered an herbarium voucher at BIGU that appeared to be a distinct taxon in Roldana La Llave (Asteraceae: Senecioneae) that did not resemble other species collected in Guatemala. A subsequent field visit to the Sierra de las Cuchumatanes in western Guatemala confirmed the discovery of the new taxon, which is described below.
Type: GUATEMALA. Huehuetenango: Sierra Cuchumatanes. Mpio. de Chiantla. Laguna Magdalena; small lagoon surrounded by disturbed forest with Abies guatemalensis, Pinus hartwegii, Cupressus lusitanica, and Baccharis vaccinioides; 2913 m; 15°32′32″N, 91°23′43″W, 10 Dec 2009, T. Sultan Quedensley 10188 with M.E. Véliz Peréz & L.E. Velásquez Méndez. (HOLOTYPE: BIGU!; ISOTYPES: CAS!; NY!; TEX!; US!)
Roldanae lanicauli (Greenm.) H. Rob. & Brettell similis sed differt petiolis glabris, paginis abaxialis foliorum glabrescentibus, pedunculis sparsim strigosis, et flosculis disci 14–18.
Rhizomatous Suffrutescent Herbs erect to scandent, 1.0–2.5 m tall; most basal stems woody, pilose, striate; young stems glabrous, striate. Leaves simple, palmately-veined, petiolate; petioles 8–18 cm long, pilose to hispidulose, trichomes tawny; blades reniform, 6–12 cm long, 8–15 cm wide, 8–12 shallow lobes, margins with callose denticles, leaf base cordate to truncate at base, adaxial surface dark green and strigulose, abaxial surface sparsely strigulose. Heads numerous, arranged in terminal rounded cymes 5–8 cm wide, ultimate peduncles 7–11 mm, floccose. Phyllaries uniseriate, 7–8, 7–8 mm long, 1–2 mm wide; brown in the center, mammilate, apex villose. Ray Florets pistillate, 7–8, 18–20 mm long, ligules yellow, 9–11 mm long, 2–4 mm wide. Disc Florets 14–18, yellow, 12–14 mm long; corolla tube 6–7 mm long. Cypselae glabrous, brown, 1–2 mm long, 8–10 ribs; pappus of numerous white bristles; 7–8 mm long.
Roldana is distributed from the Arizona-Mexico border to Panama, with most species occurring at elevations between 1500–3000 meters (Funston, 2008). The genus of herbs, shrubs, and small trees consists of 49 species and is a common floral component of montane ecosystems, especially in Central to Southern Mexico and Guatemala.
Roldana riparia is morphologically similar to R. lanicaulis with its reniform leaves but differs from this taxon in having 7–8 phyllaries versus 10–13 in the latter species, 14–18 disk florets versus 7–12, and the abaxial leaf surfaces are sparsely strigulose while in R. lanicaulis the abaxial surfaces are lanate tomentose. The other species in Guatemala do not have reniform leaves. Ecologically, this new species is unique in the genus as the three known populations occur immediately adjacent to a water source (Fig. 3). No other species in the genus always occurs so close to water sources.
Distribution and Habitat. Guatemala, Huehuetenango; Roldana riparia occurs in the Sierra Cuchumatanes along streams and standing bodies of water in disturbed montane forests with Abies guatemalensis, Pinus hartwegii, Cupressus lusitanica, and Baccharis vaccinioides at elevations of 2500–2900 m. The plants, including seedlings, have not been observed more than 5 m from a water source.
Etymology. The Latin epithet refers to the riparian habitats in which this plant occurs with its “roots in the water.”
Additional specimens examined: GUATEMALA. Huehuetenango: Sierra Cuchumatanes. Mpio. de Chiantla. Laguna Magdalena; 2913 m; 15°32′32′N, 91°23′43″W, 10 Dec 2009, M.E. Véliz Pérez 21098 with T. Sultan Quedensley & L.E. Velásquez Méndez. (BIGU; F; MO; TEX); Mpio. San Mateo Ixtatán; 2538 m; 15°50′23.7′N, 91°28′50.9″W, 4 Feb 2011, M.E. Véliz Pérez 22460 with & L.E. Velásquez Méndez (BIGU; US); Mpio. San Juan Ixcoy. 2700 m; 15°33′29.22′N, 91°25′22.26″W, 18 April 2009, P. Bourgoin 20 with S. Montpetit. (BIGU).
Key to the species of Roldana from Guatemala
1a. Leaf blade venation pinnate.
2a. Leaves abaxially glabrous; phyllaries 5–6R. schaffneri
2b. Leaves abaxially lanate tomentose; phyllaries 10–13R. barba-johannis
1b. Leaf blade venation palmate.
3a. Leaf blades peltateR. heterogama
3b. Leaf blades marginally attached
4a. Phyllaries 7–8
5a. Leaf lobes deeply cut forming rectangular segmentsR. greenmanii
5b. Leaf lobes shallowly cut
6a. Leaf lobes rounded; ultimate peduncles 8–20 mm longR. petasitis
6b. Leaf lobes, acute; ultimate peduncles 2–6 mm long
7a. Phyllaries glabrousR. acutangula
7b. Phyllaries pubescent
8a. Leaves with 5–7 lobes; ovate to palmatifidR. jurgensenii
8b. Leaves with 8–12 lobes; reniformR. riparia
4b. Phyllaries 10–13
9a. Heads 12–20 mm long, disk florets ca. 30; white latex presentR. gilgii
9b. Heads 8–12 mm long disk florets 10–20; latex absent
10a. Leaf blades ovate to rotundR. aschenborniana
10b. Leaf blades reniformR. lanicaulis
Only the three cited populations are known of Roldana riparia. Prior to this discovery, ten species of Roldana had been collected in Guatemala. Two species, R. gilgii and R. greenmanii have relatively restricted geographic ranges (i.e., Chiapas, Mexico, and Guatemala) and are considered endemic (Funston, 2008; Nash & Williams, 1976).
Funding for field work was provided from The University of Texas at Austin was provided by the Plant Biology Graduate Program. Extramural funding was provided by the American Philosophical Society of America through the Lewis and Clark Field Scholar Program. We thank Billie Turner of The University of Texas at Austin Plant Resources Center for his taxonomical guidance and Tom Wendt for support in the herbarium. Guy Nesom assisted with the Latin diagnosis. Lastly, we thank Leah Dannenberg of the Department of Biological and Environmental Sciences at Georgia College for providing the excellent illustrations.