Chusquea riparia Pianiss. & L.G. Clark, 2023

Pianissola, Evandro M., Gonçalves, Ana Paula S., Clark, Lynn G. & Oliveira, Reyjane P., 2023, Morphological, geographic and ecological evidence support a new species of Chusquea subg. Swallenochloa (Poaceae, Bambusoideae, Bambuseae) from Parque Nacional do Caparaó, Brazil, Phytotaxa 600 (3), pp. 119-135 : 128-132

Chusquea riparia Pianiss. & L.G. Clark , sp. nov., Figures 2 , 3 , 4 , 5E –H, 6D–G and 7 .

Type:— BRAZIL. Minas Gerais: Alto Caparaó, Parque Nacional do Caparaó , Trilha para o Pico da Bandeira , 2104 m, 20°24’46.2”S, 41°49’43.1”W, 16 August 2015, Pianissola et al. 111 (holotype VIC!, isotype: ISC!)

Diagnosis:— Chusquea riparia differs from C. heterophylla in the following combination of characters: habit clambering or scandent when young and more or less erect but arching at the apex when mature (versus erect at the base and inclined to arching slightly at the apex), internodes 12–19 cm long (vs. 3.5–10.5 cm), culm leaves deciduous (vs. persistent), with sheaths abaxially glabrous (vs. scabrid to scabrous), blades persistent or deciduous (vs. always persistent), branching modified extravaginal (vs. extravaginal), subsidiary branches 27–98(–140) per node [vs. 12–45 (–65)], foliage leaf sheaths pubescent to densely pubescent (glabrous on the old sheaths) (vs. pubescent between the nerves and near the margins), blades abaxially pubescent with second-order veins present (vs. glabrous, without second-order veins), spikelets 7.5–9.8 long [vs. 5.4–7(–7.4) mm], glumes I and II scale-like and less than 1/12 the spikelet length (vs. developed and 1/12–1/5 the spikelet length), and glumes III and IV 3.8–7 mm long (vs. 2.9–4.3 mm).

Description:— Culms 0.6–1 cm in diameter, 2–4.5 m tall, caespitose, clambering or scandent when young and more or less erect but arching at the apex when mature; internodes 12–19 cm long, solid, terete to slightly sulcate above the branch complement becoming terete in the upper portion, glabrous or mostly glabrous with a puberulent ring below the node and the sulcus puberulent, waxy, light moss green to vinaceous when young, and yellow when mature. Culm leaves 13–25.2 cm long, longer than the internodes, deciduous as the branches develop, the juncture of the sheath and blade convex, abaxially as an obscure to evident line; sheaths 8.8–15 cm long, 1.4‒2.5 times as long as the blade, more or less rectangular, adaxially glabrous, abaxially glabrous or scabrid near the base and glabrous elsewhere, the margins glabrous or ciliate, fused at the base for ca. 3mm, sheath summit extension(s) absent or present just on one side, null‒ 1 mm long, erect, girdle 0.3‒2.5 mm wide, glabrous or pubescent, same color as the sheath; outer ligule absent; inner ligules 0.3–1.5 mm long, erose, ciliolate; blades 3.5–9.5 cm long, triangular, erect, persistent or deciduous, adaxially completely scabrid, or glabrous at the base and becoming scabrid towards the apex, abaxially mostly glabrous, apex scabrid, midrib obscure, apex mucronate or short awned, margins glabrous or scabrid, base not pseudopetiolate. Nodal line more or less horizontal or slightly inclined, dipping slightly under the bud/branch complement, supranodal ridge slightly swollen; nodal region height 3‒5(‒7) mm, bud complement 0‒1 mm above the nodal line; central bud apex triangular and base rounded, subtended by 15‒40 subsidiary buds, in 1‒2(‒3) rows, in a semicircular (constellate) array, usually subequal or rarely 2 more robust, one on each side of the central bud. Branching modified extravaginal; central branch length not observed, 2‒6 mm in diam., curving upwards and away from the main culm at a 45° angle, rebranching; 27‒98(‒140) subsidiary branches per node, usually subequal or rarely 2 branches more robust flanking the central branch and the rest subequal, becoming shorter and less robust from the central branch, rebranching or not, 4‒20 cm long, subequal branches 0.5‒1 mm in diam., the robust branches 1‒1.9 mm in diam., horizontal to erect. Foliage leaves 7–16(–19) per complement on vegetative branches, 2‒4 per complement on reproductive branches; sheaths persistent, uniform in color, pubescent to densely pubescent, or glabrous on the old sheaths, nerves prominent or slightly prominent, not keeled or slightly keeled near the apex, margins ciliate or glabrous, ciliate at the apex in the junction sheath/inner ligule (glabrous on old sheaths), summit extension(s) absent or present, null–0.3(‒0.5) mm long, pubescent as the sheath; outer ligule (0.05‒) 0.1–0.2 mm long, a minute rim, erect, glabrous or rarely ciliolate; inner ligule 0.1–0.3 mm long, truncate, glabrous or puberulent; pseudopetiole 0.2–0.8 mm long, distinct, adaxially glabrous, adaxially scabrous or glabrous; blades 1.7–5.1 × 0.15–0.45 cm and L:W=(4‒)7‒12(‒14) on vegetative branches, (1‒)1.3‒4.2 × 0.2‒0.45 and L:W=4.5–9.5 on reproductive branches, adaxially scabrous over some veins, or completely glabrous, abaxially pubescent, not tessellate, midrib slightly eccentric, distinguishable for 1/2‒3/4 of the blade length, second-order veins present, 2‒3 on each side of the blade, lanceolate, base asymmetric, cuneate-narrowly cuneate or rounded-cuneate, apex navicular, short-subulate to subulate, tip (0.5‒) 1‒2 mm long, margins scabrous or scabrid. Synflorescences 1.5‒4.5 × 0.4‒0.7 cm, paniculate, narrow, not interrupted, base retained within the subtending sheath; rachis angular, puberulent to densely puberulent; branches 1.2‒2 cm long, appressed; pedicels 2‒8 mm long, angular, puberulent, erect. Spikelets 7.5‒9.8 × ca. 1.5 mm, more or less terete; glumes I and II, scale-like, nerves absent, abaxially glabrous, apically not ciliate (glabrous); glume I 0.1‒0.5 mm long, <1/20 the spikelet length; glume II 0.2‒ 0.8 mm long, <1/12 the spikelet length; glumes III and IV 1/2‒2/3 the length of the spikelet, abaxially puberulent or glabrous (trichomes deciduous), margins ciliate near the apex, keeled, awned; glume III 3.8‒7 mm long including the awn, 3‒5.3 mm excluding the awn, awn 0.8‒1.7 mm long, 3‒5-nerved; glume IV 4‒7 mm long including the awn, 3.2‒ 4.5 mm long excluding the awn, awn 0.8‒1.8 mm long, (3‒)5(–7)-nerved; lemma 7.3‒9.8 mm long including the awn, short-awned to awned, awn 0.8‒1.5 mm long, 7‒9-nerved, keeled, abaxially glabrous to short-puberulent, margins ciliate near the apex or not; palea 7.8‒9.5 mm long, shorter to longer than the lemma, bimucronulate or bimucronate, abaxially glabrous at the base gradually becoming incanous to puberulent towards the apex, on the upper 1/2 or less, sometimes the sulcus scabrid, 4-nerved, 2-keeled, sulcate for the upper 1/2, margin ciliolate near the apex, or not. Lodicules 3, apically ciliate, glabrous; the anterior pair ca. 1.5 mm long, the posterior one 0.8‒1.3 mm long. Stamens 3; anthers 3‒4 mm long, yellow. Fruit unknown.

Etymology: —The specific epithet “ riparia ” refers to the characteristic habitat, along streams, of this species.

Taxonomic comments —Mature individuals of Chusquea riparia exhibit the shrubby habit, short and waxy internodes, narrow and short leaves, and contracted paniculate synflorescences that allow us to place it in C. subg. Swallenochloa . Although the modified extravaginal branching and the spikelet morphology suggest its placement in the C. nudiramea informal group, the usually subequal branches and foliage leaf sheath indument and persistence do not match with the other members of this group. On the other hand, the usually subequal branches could allow the placement of C. riparia in the C. culeou or C. heterophylla groups, but again, other characters do not match, like the extravaginal branching pattern/persistent culm leaves, the foliage leaf sheath with a pubescent strip, and the spikelet morphology. Given such incongruence, we place C. riparia as Incertae Sedis within the subgenus. With the description of C. riparia , C. subg. Swallenochloa now comprises 52 species, and Chusquea as whole has 204 species.

Three other small- or narrow-leaved species of Chusquea subg. Swallenochloa occur in sympatry, in the Parque Nacional do Caparaó, with C. riparia : C. baculifera Silveira (1919: 99) , C. caparaoensis Clark (1992: 408) and C. pinifolia (Nees in Martius 1829: 525) Nees (1835: 490). Although these sympatric species could be considered similar, C. riparia is the only species in this location that has the foliage leaf blades abaxially pubescent, foliage leaf sheaths completely pubescent, and subsidiary branches in a constellate array and usually subequal (rarely with only two robust branches and the rest subequal).

Phenology: —EPM and APSG collected specimens of Chusquea riparia in 2015, when many young individuals were seen, as well as one flowering clump and a few adult vegetative clumps. These observations allowed us to infer that a reproductive event happened some time before 2015 because of the extensive presence of young individuals, but due to the absence of data related to the growth and development of this species, we cannot estimate when the gregarious flowering happened. The flowering and adult clumps probably represent asynchronous individuals. Another reproductive collection was made in 1997 (Leoni 3613, RB), but no mention about mass flowering is indicated in the label data. If this collection also represents a gregarious event and no reproductive events occurred between these two records, we could infer a flowering cycle of approximately 15 years.

Additional specimens examined (paratypes):— BRAZIL. Espírito Santo: Iúna, Parque Nacional do Caparaó , Vale Encantado , 25 January 1997, Leoni 3613 (fl.) ( RB); ibid., 2025 m, 20 June 2005, Leoni et al. 6206 ( HUEFS, RB) . Minas Gerais: Alto Caparaó, Parque Nacional do Caparaó , Arrozal , 2300 m, 9 January 1999, Leoni 4093 ( HUEFS, RB); Cachoeira Bonita , 1684 m, 8 April 2016, Pianissola et al. 138 ( HUEFS, ISC, VIC); ibid., 1641 m, 20º24’19.9”S, 41º50’13.4”W, 26 February 2016, Costa et al. 96 ( HUEFS, VIC), Trilha para o Pico da Bandeira , 2104 m, 20°24’46.2”S 41°49’43.1”W, 16 August 2015, Pianissola et al. 110, 112 (fl.) ( HUEFS, ISC, VIC); Vale Encantado , 1997 m, 20°24’39.2”S 41°50’03.6”W, 9 April 2015, Pianissola et al. 79 ( HUEFS, ISC, VIC); ibid., 2040 m, 20°24’44.9”S 41°49’58.0”W, 16 August 2015, Pianissola et al. 113*, 114* ( HUEFS, ISC, VIC); ibid., 1854 m, 8 April 2016, Pianissola et al. 134 ( HUEFS, ISC, VIC); Espera Feliz, Cachoeira da Farofa , 1906 m, 20º28’18.8”S, 41º49’44.2”W, 4 April 2017, Pianissola et al. 155 ( HUEFS) .

Examined specimens of Chusquea heterophylla :— BRAZIL. Sello s.n. ( US 1021584). Minas Gerais: Araponga, Parque Estadual da Serra do Brigadeiro , Trilha do Pico do Boné , 1825 m, 20º41’10.2”S, 42º26’39.7”W, 05 December 2013, Pianissola 32* (HUEFS, VIC); ibid., 06 February 2019, Pianissola 280 (fl.), 281 (fl.) ( HUEFS); ibid., 28 August 2015, Silva & Pianissola 293, 294, 295, 296* (fl.) ( HUEFS, VIC); Itamonte, Parque Estadual da Serra do Papagaio , Pico da Boa Vista , 22°17’33.0”S, 44°45’0.7”W, 2137 m, 7 November 2007, Viana et al. 3186* ( BHCB); ibid., road to Pico das Agulhas Negras , Km 13-14, Fazenda Alsene , 2400 m, 16 January 1990, Clark & Morel 634 ( BHCB, ISC, K, RB, SJRP, SP, US); ibid., Parque Nacional de Itatiaia , Pico das Agulhas Negras , near abrigo Rebouças , Rio Campo Belo , 2300 m, 22º23’S, 44º38’W, 10 February 1990, Clark et al. 658 (fl.) ( ISC, K, MO, NY, RB, SJRP, SP, US). Rio de Janeiro: Nova Friburgo, Pico da Caledônia , 2250 m, 22°21’13.0”S, 42°35’11.8”W, 24 January 2019, Pianissola 224 (fl.), 225 (fl.), 226 (fl.) ( HUEFS); ibid., Reserva do Petrobras , Serra dos Órg„os , 2100 m, 22º22’S, 42º36’W, 15 February 1991, Clark et al 803 ( ISC, K, MBM, MO, SJRP, SP, US) and Clark et al. 804 (fl.) ( ISC, MBM, MO, SJRP, SP, US). Petrópolis / Teresópolis, Serra dos Órg„ os, Morro Açu , 4 April 1972, Soderstrom et al. 1928* (fl.) ( RB, US); Resende, Parque Nacional do Itatiaia , Planalto do Itatiaia , 2494 m, 22º22’50.3”S, 44º39’56.0”W, 30 January 2019, Pianissola 261 (fl.) ( HUEFS); ibid., 2494 m, 22º23’5.1”S, 44º40”42.0”W, 30 January 2019, Pianissola 268, 269 (fl.) ( HUEFS); ibid., 07 November 2003, Santos et al. 569* (fl.) ( HUEFS, VIC); shelter house to Pedra Altar , Tryon & Tryon 6692* ( US); Teresópolis, Parque Nacional da Serra dos Órg„os , Campo das Antas , trail to Pedra do Sino , 11 February 1991 Clark et al. 791 ( ISC, MBM, MO, RB, SJRP, SP, US) and Clark et al. 792 (fl.) ( ISC, MO, RB, SJRP, SP, US); Pedra do Sino , 26 January 2019, Pianissola 236 (fl.) ( HUEFS); ibid., Parque Estadual da Serra do Órg„os , trilha da Pedra do Sino , 2158 m, 22º20’31.0”S, 43º01’41.0”W, 12 March 2002, Santos et al. 489* (fl.) ( HUEFS, VIC); Haut des Orgues , 1872 (fl.), Glaziou 6444* (fl.) ( RB, US) .

Key to the species of Chusquea subg. Swallenochloa in the Parque Nacional do Caparaó, Brazil (based on vegetative characters)

2. Branching modified extravaginal; foliage leaf sheaths deciduous, strigillose, foliage leaf blades (3‒)3.5‒6.8 × (0.15‒)0.18‒0.27 cm ............................................................................................................................................................................... C. caparaoensis

- Branching intravaginal; foliage leaf sheaths persistent, puberulent or a pubescent strip near the margin, foliage leaf blades 1.5‒3.5 × 0.08‒0.12 cm .................................................................................................................................................................. C. pinifolia

3. Branching intravaginal, (6‒)10‒14(‒19) subsidiary branches per node; foliage leaf blades abaxially glabrous............ C. baculifera

- Branching modified extravaginal, 27‒98(‒140) subsidiary branches per node; foliage leaf blades abaxially pubescent................... .............................................................................................................................................................................................. C. riparia

Figures

FIGURE 2. Chusquea riparia habitat and habit. A–C. Young individuals with clambering habit growing on the surrounding vegetation, in a riparian area (white square is shown close-up in B). D. Habit initially erect and leaning on the surrounding vegetation. E. Erect habit with arching apex; C. pinifolia (lower right) co-occurring with C. riparia. White arrowheads indicate C. riparia in the vegetation. (Photos by Evandro Pianissola).

FIGURE 3. Chusquea riparia.A–B.Culms and branches.C.Young culm showing modified extravaginalbranching and culm leaf releasing itself (above) and one deciduous culm leaf blade (below). D. Synflorescence and foliage leaf blades. (Photos by Evandro Pianissola).

FIGURE 4. Chusquea riparia. A. Culm segment with a nodal region showing branching pattern, branches, foliage leaves, and culm leaf in situ. B. Culm leaf adaxial view. C. Bud complement. D. Foliage leaf with sheath and the base of the blade. E. Reproductive branch with a terminal synflorescence. F. Spikelet (A–C Pianissola et al. 114, D Pianissola et al.155, E–F Leoni 3613). Illustration by Pétala G. Ribeiro.

FIGURE 5. Morphological comparison between Chusquea heterophylla (A–D) and C. riparia (E–H). A. Ligular area. B. Foliage leaf sheath indument. C. Foliage leaf blade abaxial surface. D. Spikelet. E. Ligular area. F. Foliage leaf sheath indument. G. Foliage leaf blade abaxial surface. H. Spikelet. Black bars= 1 mm. (A and C Pianissola 235, B and D Pianissola 225, E–G Pianissola et al. 155, H. Leoni 3613).

FIGURE 6. Micromorphology of the abaxial surface of the foliage leaf blade of Chusquea heterophylla and C. riparia as seen with SEM. A–C C. heterophylla. D–G C. riparia (A–B. Pianissola 32. C. Viana et al. 3186. D. Pianissola et al. 113; E. and G. Pianissola et al. 114; F. Pianissola et al. 111). White oval = stomatal apparatus; White bar A and D = 40µm; B, E and F = 10 µm; C and G = 5 µm) (bm= bicellular microhair; ma= macrohair; pa= papillae of the long cell; pr= prickle hair; ps= papillae of the subsidiary cell; sc= silica cell; st= stomata).

FIGURE 7. Distribution map of Chusquea heterophylla and C. riparia. Red square= placement of the main map in Brazil. ES= Espírito Santo, RJ= Rio de Janeiro, MG=Minas Gerais, SP=S„o Paulo.