Rhipidocladum singuliflorum Ruiz-Sanchez & C.D.Tyrrell, 2022

Ruiz-Sanchez, Eduardo, Tyrrell, Christopher D., Carrillo-Reyes, Pablo & Nuno-Rubio, A. T., 2022, A striking new species of Rhipidocladum (Poaceae: Bambusoideae: Bambuseae: Arthrostylidiinae) with single, terminal-spikelet synflorescences, endemic to Jalisco, Mexico, Plant Ecology and Evolution 155 (3), pp. 417-424 : 417

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Rhipidocladum singuliflorum Ruiz-Sanchez & C.D.Tyrrell

sp. nov.

Rhipidocladum singuliflorum Ruiz-Sanchez & C.D.Tyrrell sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4


MEXICO - Jalisco • Puerto Vallarta, Rio Palo Maria ; 20°33 ’8.76” N, 105°15 ’34” W; 6 m; 10 Dec. 2021; fl.; E. Ruiz-Sanchez, A.T. Nuño, A. Zabalgoitia, L.A. Monroy & L. Campos 722; holotype: IBUG; isotypes: MEXU, ZEA GoogleMaps .


Rhipidocladum singuliflorum differs from R. barbinode and R. racemiflorum by having a single terminal spikelet. Meanwhile, R. barbinode has a spicate synflorescence with 3-7 spikelets and R. racemiflorum has a raceme synflorescence with 10-13 spikelets. R. singuliflorum has efimbriate or poorly developed fimbriae on the foliage leaves, meanwhile, R. barbinode and R. racemiflorum bear fimbriae at the apex of the sheath of the foliage leaves.


Culm height 3-10 m. Internodes smooth, uniform in colour, 9-33 cm long, 3-9 mm in diameter, hollow (pithy when young); walls 2-3 mm thick. Culm leaves 17-19 cm long; sheaths (6.5-)7.6-9(-9.9) cm long, abaxially glabrous, adaxially glabrous and shiny; blades erect, 9-10 cm long, abaxially sparsely pubescent at the base, adaxially glabrous, margins entire; fimbriae not seen. Branch complements at mid-culm nodes with (30-)41-87(-120) branchlets; branchlets (8-)13-30(-50) cm long, glabrous or pubescent. Foliage leaves 3-4 observed on flowering branchlets; sheaths 9-22 mm long, abaxially pubescent (occasionally glabrous); mostly efimbriate, when fimbriate 0.2-0.8 mm long, white to stramineous; pseudopetioles 1.0-1.6 mm long, abaxially and adaxially pubescent; blades lanceolate to narrowly ovate with an attenuate apex, 32-75 mm long, 5-7 mm wide, abaxially and adaxially glabrous, without sparse patches of white cilia near the base on the abaxial side. Synflorescences 2.0-3.4 cm long, 0.9-10 mm wide, composed of a single spike, sometimes develop two spikelets, one of them with only two florets; rachis pubescent. Spikelets 2.0-3.4 cm long, comprising 2-4 glumes and (2-)4-5(-20) fertile florets, rachilla joints 3.5-4 mm long, glabrous. Glumes pubescent margins ciliate, awnless, lower glume, 3.2-5.8 mm long, 6-, 9-, 10-nerved, lanceolate; upper glume, 4.8-7.0 mm long, 11-, 13-nerved, lanceolate. Lemmas 8.8-12.0 mm long, 9-, 13-nerved, ovate and inflated, pubescent, apex rounded-obtuse and muticous. Palea 10.0-13.6 mm long, keels and sulcus pubescent, apex rounded-obtuse and muticous. Lodicules 3, abaxially glabrous, hyaline, margin ciliate apex fimbriate, the anterior pair 2.6-3.2 mm long, the posterior one 2.0-2.4 mm long. Anthers 3. Ovary 1.0-1.5 mm long, stigmas 2, plumose. Caryopsis 3.3-3.5 mm long, ellipsoid, pubescent with trichomes near base and apex, indented on hilum side, yellowish-golden.


This species is only known from three localities in the municipality of Puerto Vallarta, Jalisco, Mexico in the Jalisciense-Tuito district of the Sierra Madre del Sur ( Santiago-Alvarado et al. 2016) (Fig. 1 View Figure 1 ).

Habitat and ecology.

This species inhabits the slopes of humid canyons of creeks and rivers at 6-150 m a.s.l. The vegetation corresponds to subdeciduous and tropical dry forests with associated species, such as Astronium graveolens Jacq., Bursera spp., Casearia arguta Kunth, Cecropia obtusifolia Bertol., Cnidoscolus tepiquensis (Cost. & Gall.) Lundell, Croton schiedeanus Schltdl., Cupania dentata Moc. & Sesse, Dendropanax arboreus (L.) Decne. & Planch., Euphorbia spp., Ficus spp., Guettarda elliptica Sw., Inga laurina (Sw.) Willd., Lonchocarpus spp., Luehea candida Mart., Lysiloma divaricatum (Jacq.) Benth., Ouratea madrensis L.Riley, Pseudobombax ellipticum (Kunth) Dugand, and Zygia conzattii (Standl.) Britton & Rose, among others (Fig. 3A View Figure 3 ).


Latin singulus, solitary, and florum, flowered, alluding to usual occurrence of single, terminal spikelet in synflorescence (Figs 2A View Figure 2 , 3D-F View Figure 3 ). The use of - florum instead of - spiculum is preferred here [cf. R. racemiflorum ].

Preliminary IUCN conservation assessment.

Critically endangered: CR B1ab(iii). Rhipidocladum singuliflorum is known from three localities that are separated by no more than 14 km. Using GeoCAT, the Extent of Occurrence (EOO) was calculated to be 10.6 km2, and the Area of Occupancy to be 12 km2, based on 2 × 2 km cells. The three localities are canyons that are not suitable for agriculture or grazing, and are often used for recreation with one of them (El Nogalito) currently under management by an ecotourism centre. The localities, however, are adjacent to the Carretera Pacífico (Carretera Federal 200), the major west coast highway, and potentially in the path of the planned series of “vía corta" highway expansions. A preliminary category of Critically endangered: CR B1ab(iii) is proposed following the IUCN ( IUCN Standards and Petitions Committee 2022) criteria.

Additional specimens examined.

MEXICO - Jalisco • Puerto Vallarta, 4 km al SE de Playa Grande, subiendo por el Río Pitillal (2.4 km en línea recta); 20°38 ’14” N, 105°10 ’14” W; 120 m; 18 Feb. 2022; fl.; P. Carrillo-Reyes & S. Quijas-Fonseca 10093; IBUG • Arroyo El Nogalito, 0.8 km en línea recta al SE del Ecoparque El Nogalito; 20°33 ’24” N, 105°14 ’10” W; 130 m; 20 Mar. 2022; P. Carrillo-Reyes & A.T. Nuño-Rubio 10106; IBUG • Rio Palo Maria ; 20°33 ’8.76” N, 105°15 ’34” W; 6 m; 16 Nov. 2021; fl.; A.T. Nuño & L. Campos s.n.; IBUG GoogleMaps .