Chusquea enigmatica emend. Ruiz-Sanchez, Mejía-Saulés, Cortés & L.G. Clark, 2014

Ruiz-Sanchez, Eduardo, Castro-Castro, Arturo & Clark, Lynn G., 2022, A new informal group in Chusquea subg. Swallenochloa (Poaceae: Bambusoideae: Bambuseae) and emended descriptions for the Mexican endemics C. enigmatica and C. septentrionalis, Phytotaxa 554 (1), pp. 47-58 : 48-50

Chusquea enigmatica emend. Ruiz-Sanchez, Mejía-Saulés, Cortés & L.G. Clark

TYPE:— MEXICO. Veracruz: cima del volcán de Acatlán sobre el anillo de la parte sureste, suelo negro, planta estéril, bosque de Fagus grandifolia Ehrhart (1788: 22) con Podocarpus matudae Lundell (1937: 212) , 19°47’48.2’’ N, 100°41’42.3’’ W, 1960 m, 19 February 2013, E. Ruiz-Sanchez & T.M. Mejía-Saulés 434a (holotype: XAL!, isotypes: IEB!, ISC!, MEXU!) .

Description:—Rhizomes leptomorph, 0.4–1 m long. Culms 0.2–2 m tall, 0.5–5 mm in basal diameter, erect, decumbent and geniculate. Internodes 10–35 mm long, 12–15 per culm, terete, glabrous, green, solid. Culm leaves 23–48 mm long, glabrous, straw-colored, deciduous as branches develop; sheaths 18–39 mm long, rectangular with rounded shoulders, 4–6 times as long as the blade, the margins entire or ciliate on both sides, glabrous; blades 3–9 mm long, narrowly triangular, erect, deciduous, apex acuminate, margins entire or slightly ciliate, glabrous; girdle not developed, inner ligule 0.2–0.5 mm long, glabrous, truncate. Nodes at mid culm with 1–3 buds, composed of one larger triangular central bud subtended by 1–2 slightly smaller triangular, closely adjacent subsidiary buds arranged in a single line; nodal line horizontal, supranodal ridge present and prominent. Branching extravaginal or intravaginal on the same culms, the sheaths deciduous, 1–3 branches per node, diverging from the main culm at 45°, 90–150 mm long, 1–1.5 mm in diameter, some rebranching. Foliage leaves (5–)6–9(11) per complement; sheaths glabrous, the summit short ciliate; leaf blades 100–117 mm long, 0.8–12 mm wide, L:W = 8–14, abaxially glaucous and adaxially green, glabrous, not tessellate, the base oblique, the apex apiculate, the margin finely scabrous on both sides; pseudopetioles 1–1.5 mm long, adaxially and abaxially glabrous, inner ligule 2–3 mm, rounded; outer ligule to 0.2–0.3 mm long, glabrous or finely ciliate. Synflorescences 6–120 mm long, 4–110 mm wide, open, paniculate; rachis angular, slightly scabrous; branches spreading, the lower ones 3–65 mm long, angular, scabrous; pedicels (1–)3–5(–9) mm long, angular, scabrous. Spikelets 6.8–7.4 mm long, 0.9–1.2 mm wide, laterally compressed. Glumes I and II ovate, obtuse, margin entire, scabrous, enervate; glume I 0.4–0.7 mm long, 1/20–1/10 the spikelet length; glume II 0.5–0.7 mm long, 3/50–1/10 the spikelet length. Glumes III and IV glabrous, scabrous toward the apex, 1-nerved, awned, margin ciliate toward the apex; glume III including the awn 2.8–3.8 mm long, the awn 0.5–0.6 mm, 2/5–1/2 the spikelet length; glume IV including the awn 3.2–4 mm long, the awn 0.4–0.7 mm long, ca. 1/2 the spikelet length. Lemmas 6.6–7.4 mm long, 5– nerved, green becoming purplish, scabridulous, awned, margin ciliate to the apex; awn 0.5–0.6 mm long. Paleas 6.4–7 mm long, 2–nerved, scabridulous; nerves scabrous, apex biapiculate, the sulcus scabridulous. Lodicules 3, 1.1–1.4 mm long, glabrous, hyaline, margin ciliate, cilia hyaline. Stamens and stigmas not seen. Fruit not seen ( Fig. 1 ).

Habitat and distribution:— Chusquea enigmatica was described from a single locality in Veracruz state in a montane cloud forest dominated by Fagus grandiflora and Podocarpus matudae at 1960 m ( Ruiz-Sanchez et al. 2014a). However, new collections were made from Hidalgo and San Luis Potosí ( Figs. 2 , 3 ) in montane cloud forest at elevations of 1738–2015 m.

Comparison:—Synflorescences and spikelets of Chusquea enigmatica are similar to those of C. lanceolata ( Table 1 ). However, although the primary synflorescence branches in both species are spreading, all higher-order branchlets and pedicels in C. lanceolata are appressed to the primary branches, whereas in C. enigmatica , these are also spreading. The sizes of glumes I, II, III and IV are somewhat larger in C. lanceolata , and the abaxial indument is different. Chusquea enigmatica has scabrous and awned glumes III and IV, and these are pubescent below the apex and subulate in C. lanceolata . Glume IV is 1-nerved in C. enigmatica and 3-, 5- or 7-nerved in C. lanceolata , and the lemma is 5-nerved in C. enigmatica and 7- or 9-nerved in C. lanceolata ( Table 1 ).

Etymology:—The specific epithet refers to the unusual morphology with leptomorph rhizomes and reduction in bud and culm sizes and the consequent difficulty in classifying this species within one of the known sections of Chusquea .

Phenology:— The first known flowering record for this species occurred during the summer of 2019 (S. Zamudio, J. Ceja & A. Mendoza 17454).

Specimens examined:— Hidalgo: Tianguistengo, km 3 del camino Tianguistengo-Zacualtipán. Límites municipales de Zacualtipán y Tianguistengo, 20°42’21.74’’N, 98° 38’46.3’’W, 1789 m, 19 abril 2018, D. S. Figueroa & D. Juárez 217 (IBUG); cueva de El Diablo, 20° 42’ 19.95’’N, 98° 38’ 52.98’’W, 1830 m, 10 agosto 2018, E. RuizSanchez & D. Ramos 616 (IBUG). San Luis Potosí: Xilitla, La Trinidad, 21°24’ 39.78’’N, 99°03’52.8’’W, 1805 m, 27 abril 2017, B. Tellez & Y. Rico 3 (IEB); ejido La Trinidad, sendero que va a la cueva, 21°24’45’’N, 99°04’4.45’’W, 2015 m, 6 octubre 2017, J.P. Brunel et al. 334 (IBUG); camino del poblado La Trinidad al Llano de La Garza , 21°24’56”N, 99°04’49”W, 2051 m, 2, julio 2017, S. Zamudio et al. 17230 (IBUG); camino de La Trinidad al Llano de la Garza, 21° 24’39.78’’N, 99°03’52.8’’W, 1890 m, 3 julio 2017, J. Hernández Rendón et al. 118 (IBUG); ca. del Mirador, cerro La Silleta, 21°26’38’’N, 99°03’38’’W, 1738 m, 5 julio 2019 (fl), S. Zamudio, J. Ceja & A. Mendoza 17454 (IBUG) .

Figures

FIGURE 1. Chusquea enigmatica. A. Synflorescence. B. Spikelet. C. Lower glumes (I, II). D. Upper glumes (III, IV). E. Lemma (left) and palea (right). Based on S. Zamudio, J. Ceja & A. Mendoza 17454. Illustration by Juvenal Aragón Parada.

FIGURE 2. Geographical distribution map of Chusquea enigmatica and C. septentrionalis. Black squares belong to C. enigmatica, black triangles are localities of C. septentrionalis. Black arrows indicate the type locality for each species. Dotted line indicates previous northernmost Chusquea collections.

FIGURE 3. Chusquea enigmatica. A. Plants of C. enigmatica in the understory of the montane cloud forest in the State of San Luis Potosí, Mexico. B. Plants of C. enigmatica growing in a clearing of the montane cloud forest in the State of Hidalgo, Mexico. C. Leptmorph rhizome. D-E. Branches and foliage leaves from Hidalgo (D) and San Luis Potosí (E). A, E. Photos by Julián Hernández Rendón. B-D. Photos by Eduardo Ruiz-Sanchez.